Abstract

A heterostructured AlxGa1-xAs/GaAs photocathode consisting of a composition-graded buffer layer and an exponential-doped emission layer is developed to improve the photoemission performance over the wavelength region of interest. The theoretical quantum efficiency models for reflection-mode and transmission-mode AlxGa1-xAs/GaAs photocathodes are deduced based on one-dimensional continuity equations, respectively. By comparison of simulated results with conventional quantum efficiency models, it is found that the multilevel built-in electric field can effectively improve the quantum efficiency, which is related to the buffer layer parameters and cathode thicknesses. This special graded bandgap structure arising from the compositional grade in the buffer layer and doping grade in the emission layer would bring about the reduction of back interface recombination losses and the efficient collection of photons generating photoelectrons. Moreover, a best fit of the experimental quantum efficiency data can be achieved with the aid of the deduced models, which would provide an effective approach to evaluate internal parameters for the special graded bandgap photoemitters.

© 2015 Optical Society of America

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  1. S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
    [Crossref]
  2. J. Wehmeijer and B. van Geest, “High-speed imaging: Image intensification,” Nat. Photonics 4(3), 152–153 (2010).
    [Crossref]
  3. J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
    [Crossref] [PubMed]
  4. K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
    [Crossref]
  5. S. Karkare, L. Boulet, L. Cultrera, B. Dunham, X. Liu, W. Schaff, and I. Bazarov, “Ultrabright and ultrafast III-V semiconductor photocathodes,” Phys. Rev. Lett. 112(9), 097601 (2014).
    [Crossref] [PubMed]
  6. T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
    [Crossref]
  7. I. M. Dharmadasa, J. S. Roberts, and G. Hill, “Third generation multi-layer graded band gap solar cells for achieving high conversion efficiencies—II: Experimental results,” Sol. Energy Mater. Sol. Cells 88(4), 413–422 (2005).
    [Crossref]
  8. M. Kwon, I. Park, J. Kim, J. Kim, B. Kim, and S. Park, “Gradient doping of Mg in p-type GaN for high efficiency InGaN–GaN ultraviolet light-emitting diode,” IEEE Photonics Technol. Lett. 19(23), 1880–1882 (2007).
    [Crossref]
  9. D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
    [Crossref]
  10. Y. Zhang, B. Chang, Z. Yang, J. Niu, Y. Xiong, F. Shi, H. Guo, and Y. Zeng, “Annealing study of carrier concentration in gradient-doped GaAs/GaAlAs epilayers grown by molecular beam epitaxy,” Appl. Opt. 48(9), 1715–1720 (2009).
    [Crossref] [PubMed]
  11. W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
    [Crossref]
  12. G. Hao, F. Shi, H. Cheng, B. Ren, and B. Chang, “Photoemission performance of thin graded structure AlGaN photocathode,” Appl. Opt. 54(10), 2572–2576 (2015).
    [Crossref] [PubMed]
  13. A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
    [Crossref]
  14. M. Konagai and K. Takahashi, “Theoretical analysis of graded-band-gap gallium-aluminum arsenide/gallium arsenide solar cells,” Solid-State Electron. 19(3), 259–264 (1976).
    [Crossref]
  15. L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
    [Crossref]
  16. Y. Yang, W. Z. Yang, and C. D. Sun, “Heterostructured cathode with graded bandgap window-layer for photon-enhanced thermionic emission solar energy converters,” Sol. Energy Mater. Sol. Cells 132, 410–417 (2015).
    [Crossref]
  17. Y. Zhang, J. Niu, J. Zou, B. Chang, and Y. Xiong, “Variation of spectral response for exponential-doped transmission-mode GaAs photocathodes in the preparation process,” Appl. Opt. 49(20), 3935–3940 (2010).
    [Crossref] [PubMed]
  18. C. Feng, Y. J. Zhang, and Y. S. Qian, “Theoretical revision of quantum efficiency formula for thin AlGaAs/GaAs photocathodes,” Proc. SPIE 9270, 92701F (2014).
  19. Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
    [Crossref]
  20. W. E. Spicer, “Photoemissive, photoconductive, and optical absorption studies of alkali-antimony compounds,” Phys. Rev. 112(1), 114–122 (1958).
    [Crossref]
  21. T. Maruyama, E. L. Garwin, R. A. Mair, R. Prepost, J. S. Smith, and J. D. Walker, “Electron-spin polarization in photoemission from thin AlxGa1-xAs,” J. Appl. Phys. 73(10), 5189 (1993).
    [Crossref]
  22. C. Feng, Y. J. Zhang, Y. S. Qian, F. Shi, J. J. Zou, and Y. G. Zeng, “Photoemission characteristics of thin GaAs-based heterojunction photocathodes,” J. Appl. Phys. 117(2), 023103 (2015).
    [Crossref]
  23. M. Levinshtein, M. S. Shur, and S. Rumyanstev, Handbook Series on Semiconductor Parameters(Vol. 2). (World Scientific, 1996), pp. 1–36.
  24. H. C. Casey, D. D. Sell, and K. W. Wecht, “Concentration dependence of the absorption coefficient for n− and p−type GaAs between 1.3 and 1.6 eV,” J. Appl. Phys. 46(1), 250–257 (1975).
    [Crossref]
  25. Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
    [Crossref]
  26. G. A. Antypas, L. W. James, and J. J. Uebbing, “Operation of III-V semiconductor photocathodes in the semitransparent mode,” J. Appl. Phys. 41(7), 2888–2894 (1970).
    [Crossref]
  27. D. E. Aspnes, S. M. Kelso, R. A. Logan, and R. Bhat, “Optical properties of AlxGa1-xAs,” J. Appl. Phys. 60(2), 754–767 (1986).
    [Crossref]
  28. K. A. Costello, V. W. Aebi, and H. F. MacMillan, “Imaging GaAs vacuum photodiode with 40% quantum efficiency at 530 nm,” Proc. SPIE 1243, 99–106 (1990).
    [Crossref]
  29. Y. J. Zhang, J. Niu, J. Zhao, J. J. Zou, B. K. Chang, F. Shi, and H. C. Cheng, “Influence of exponential-doping structure on photoemission capability of transmission-mode GaAs photocathodes,” J. Appl. Phys. 108(9), 093108 (2010).
    [Crossref]
  30. G. A. Antypas, J. S. Escher, J. Edgecumbe, and R. S. Enck., “Broadband GaAs transmission photocathode,” J. Appl. Phys. 49(7), 4301 (1978).
    [Crossref]
  31. S. Moré, S. Tanaka, S. Tanaka, Y. Fujii, and M. Kamada, “Interaction of Cs and O with GaAs (100) at the overlayer–substrate interface during negative electron affinity type activations,” Surf. Sci. 527(1–3), 41–50 (2003).
    [Crossref]
  32. B. J. Stocker, “AES and LEED study of the activation of GaAs-Cs-O negative electron affinity surfaces,” Surf. Sci. 47(2), 501–513 (1975).
    [Crossref]
  33. J. A. Hutchby and R. L. Fudurich, “Theoretical optimization and parametric study of n-on-p AlxGal-xAs-GaAs graded band-gap solar cell,” J. Appl. Phys. 47(7), 3152–3158 (1976).
    [Crossref]

2015 (3)

C. Feng, Y. J. Zhang, Y. S. Qian, F. Shi, J. J. Zou, and Y. G. Zeng, “Photoemission characteristics of thin GaAs-based heterojunction photocathodes,” J. Appl. Phys. 117(2), 023103 (2015).
[Crossref]

Y. Yang, W. Z. Yang, and C. D. Sun, “Heterostructured cathode with graded bandgap window-layer for photon-enhanced thermionic emission solar energy converters,” Sol. Energy Mater. Sol. Cells 132, 410–417 (2015).
[Crossref]

G. Hao, F. Shi, H. Cheng, B. Ren, and B. Chang, “Photoemission performance of thin graded structure AlGaN photocathode,” Appl. Opt. 54(10), 2572–2576 (2015).
[Crossref] [PubMed]

2014 (3)

Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
[Crossref]

C. Feng, Y. J. Zhang, and Y. S. Qian, “Theoretical revision of quantum efficiency formula for thin AlGaAs/GaAs photocathodes,” Proc. SPIE 9270, 92701F (2014).

S. Karkare, L. Boulet, L. Cultrera, B. Dunham, X. Liu, W. Schaff, and I. Bazarov, “Ultrabright and ultrafast III-V semiconductor photocathodes,” Phys. Rev. Lett. 112(9), 097601 (2014).
[Crossref] [PubMed]

2013 (2)

S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
[Crossref]

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

2012 (1)

K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
[Crossref]

2011 (1)

Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
[Crossref]

2010 (4)

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
[Crossref]

J. Wehmeijer and B. van Geest, “High-speed imaging: Image intensification,” Nat. Photonics 4(3), 152–153 (2010).
[Crossref]

Y. Zhang, J. Niu, J. Zou, B. Chang, and Y. Xiong, “Variation of spectral response for exponential-doped transmission-mode GaAs photocathodes in the preparation process,” Appl. Opt. 49(20), 3935–3940 (2010).
[Crossref] [PubMed]

Y. J. Zhang, J. Niu, J. Zhao, J. J. Zou, B. K. Chang, F. Shi, and H. C. Cheng, “Influence of exponential-doping structure on photoemission capability of transmission-mode GaAs photocathodes,” J. Appl. Phys. 108(9), 093108 (2010).
[Crossref]

2009 (3)

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

Y. Zhang, B. Chang, Z. Yang, J. Niu, Y. Xiong, F. Shi, H. Guo, and Y. Zeng, “Annealing study of carrier concentration in gradient-doped GaAs/GaAlAs epilayers grown by molecular beam epitaxy,” Appl. Opt. 48(9), 1715–1720 (2009).
[Crossref] [PubMed]

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

2007 (1)

M. Kwon, I. Park, J. Kim, J. Kim, B. Kim, and S. Park, “Gradient doping of Mg in p-type GaN for high efficiency InGaN–GaN ultraviolet light-emitting diode,” IEEE Photonics Technol. Lett. 19(23), 1880–1882 (2007).
[Crossref]

2005 (1)

I. M. Dharmadasa, J. S. Roberts, and G. Hill, “Third generation multi-layer graded band gap solar cells for achieving high conversion efficiencies—II: Experimental results,” Sol. Energy Mater. Sol. Cells 88(4), 413–422 (2005).
[Crossref]

2003 (1)

S. Moré, S. Tanaka, S. Tanaka, Y. Fujii, and M. Kamada, “Interaction of Cs and O with GaAs (100) at the overlayer–substrate interface during negative electron affinity type activations,” Surf. Sci. 527(1–3), 41–50 (2003).
[Crossref]

2002 (1)

T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
[Crossref]

1999 (1)

W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
[Crossref]

1993 (1)

T. Maruyama, E. L. Garwin, R. A. Mair, R. Prepost, J. S. Smith, and J. D. Walker, “Electron-spin polarization in photoemission from thin AlxGa1-xAs,” J. Appl. Phys. 73(10), 5189 (1993).
[Crossref]

1990 (1)

K. A. Costello, V. W. Aebi, and H. F. MacMillan, “Imaging GaAs vacuum photodiode with 40% quantum efficiency at 530 nm,” Proc. SPIE 1243, 99–106 (1990).
[Crossref]

1986 (1)

D. E. Aspnes, S. M. Kelso, R. A. Logan, and R. Bhat, “Optical properties of AlxGa1-xAs,” J. Appl. Phys. 60(2), 754–767 (1986).
[Crossref]

1978 (1)

G. A. Antypas, J. S. Escher, J. Edgecumbe, and R. S. Enck., “Broadband GaAs transmission photocathode,” J. Appl. Phys. 49(7), 4301 (1978).
[Crossref]

1976 (2)

M. Konagai and K. Takahashi, “Theoretical analysis of graded-band-gap gallium-aluminum arsenide/gallium arsenide solar cells,” Solid-State Electron. 19(3), 259–264 (1976).
[Crossref]

J. A. Hutchby and R. L. Fudurich, “Theoretical optimization and parametric study of n-on-p AlxGal-xAs-GaAs graded band-gap solar cell,” J. Appl. Phys. 47(7), 3152–3158 (1976).
[Crossref]

1975 (2)

B. J. Stocker, “AES and LEED study of the activation of GaAs-Cs-O negative electron affinity surfaces,” Surf. Sci. 47(2), 501–513 (1975).
[Crossref]

H. C. Casey, D. D. Sell, and K. W. Wecht, “Concentration dependence of the absorption coefficient for n− and p−type GaAs between 1.3 and 1.6 eV,” J. Appl. Phys. 46(1), 250–257 (1975).
[Crossref]

1970 (1)

G. A. Antypas, L. W. James, and J. J. Uebbing, “Operation of III-V semiconductor photocathodes in the semitransparent mode,” J. Appl. Phys. 41(7), 2888–2894 (1970).
[Crossref]

1958 (1)

W. E. Spicer, “Photoemissive, photoconductive, and optical absorption studies of alkali-antimony compounds,” Phys. Rev. 112(1), 114–122 (1958).
[Crossref]

Aebi, V. W.

K. A. Costello, V. W. Aebi, and H. F. MacMillan, “Imaging GaAs vacuum photodiode with 40% quantum efficiency at 530 nm,” Proc. SPIE 1243, 99–106 (1990).
[Crossref]

Antypas, G. A.

G. A. Antypas, J. S. Escher, J. Edgecumbe, and R. S. Enck., “Broadband GaAs transmission photocathode,” J. Appl. Phys. 49(7), 4301 (1978).
[Crossref]

G. A. Antypas, L. W. James, and J. J. Uebbing, “Operation of III-V semiconductor photocathodes in the semitransparent mode,” J. Appl. Phys. 41(7), 2888–2894 (1970).
[Crossref]

Aspnes, D. E.

D. E. Aspnes, S. M. Kelso, R. A. Logan, and R. Bhat, “Optical properties of AlxGa1-xAs,” J. Appl. Phys. 60(2), 754–767 (1986).
[Crossref]

Bakin, V. V.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

Bargatin, I.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
[Crossref]

Bartnik, A.

S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
[Crossref]

Bazarov, I.

S. Karkare, L. Boulet, L. Cultrera, B. Dunham, X. Liu, W. Schaff, and I. Bazarov, “Ultrabright and ultrafast III-V semiconductor photocathodes,” Phys. Rev. Lett. 112(9), 097601 (2014).
[Crossref] [PubMed]

S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
[Crossref]

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
[Crossref]

Bhat, R.

D. E. Aspnes, S. M. Kelso, R. A. Logan, and R. Bhat, “Optical properties of AlxGa1-xAs,” J. Appl. Phys. 60(2), 754–767 (1986).
[Crossref]

Boulet, L.

S. Karkare, L. Boulet, L. Cultrera, B. Dunham, X. Liu, W. Schaff, and I. Bazarov, “Ultrabright and ultrafast III-V semiconductor photocathodes,” Phys. Rev. Lett. 112(9), 097601 (2014).
[Crossref] [PubMed]

Brachmann, A.

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
[Crossref]

Casey, H. C.

H. C. Casey, D. D. Sell, and K. W. Wecht, “Concentration dependence of the absorption coefficient for n− and p−type GaAs between 1.3 and 1.6 eV,” J. Appl. Phys. 46(1), 250–257 (1975).
[Crossref]

Chang, B.

Chang, B. K.

Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
[Crossref]

Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
[Crossref]

Y. J. Zhang, J. Niu, J. Zhao, J. J. Zou, B. K. Chang, F. Shi, and H. C. Cheng, “Influence of exponential-doping structure on photoemission capability of transmission-mode GaAs photocathodes,” J. Appl. Phys. 108(9), 093108 (2010).
[Crossref]

Chen, X. L.

Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
[Crossref]

Cheng, H.

Cheng, H. C.

Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
[Crossref]

Y. J. Zhang, J. Niu, J. Zhao, J. J. Zou, B. K. Chang, F. Shi, and H. C. Cheng, “Influence of exponential-doping structure on photoemission capability of transmission-mode GaAs photocathodes,” J. Appl. Phys. 108(9), 093108 (2010).
[Crossref]

Clendenin, J. E.

T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
[Crossref]

Costello, K. A.

K. A. Costello, V. W. Aebi, and H. F. MacMillan, “Imaging GaAs vacuum photodiode with 40% quantum efficiency at 530 nm,” Proc. SPIE 1243, 99–106 (1990).
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Crabb, D. G.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

Cultrera, L.

S. Karkare, L. Boulet, L. Cultrera, B. Dunham, X. Liu, W. Schaff, and I. Bazarov, “Ultrabright and ultrafast III-V semiconductor photocathodes,” Phys. Rev. Lett. 112(9), 097601 (2014).
[Crossref] [PubMed]

S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
[Crossref]

Day, D. B.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

Desikan, T.

T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
[Crossref]

Dharmadasa, I. M.

I. M. Dharmadasa, J. S. Roberts, and G. Hill, “Third generation multi-layer graded band gap solar cells for achieving high conversion efficiencies—II: Experimental results,” Sol. Energy Mater. Sol. Cells 88(4), 413–422 (2005).
[Crossref]

Dimitrov, D.

S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
[Crossref]

Dowell, D. H.

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
[Crossref]

Dunham, B.

S. Karkare, L. Boulet, L. Cultrera, B. Dunham, X. Liu, W. Schaff, and I. Bazarov, “Ultrabright and ultrafast III-V semiconductor photocathodes,” Phys. Rev. Lett. 112(9), 097601 (2014).
[Crossref] [PubMed]

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
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Edgecumbe, J.

G. A. Antypas, J. S. Escher, J. Edgecumbe, and R. S. Enck., “Broadband GaAs transmission photocathode,” J. Appl. Phys. 49(7), 4301 (1978).
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Enck, R. S.

G. A. Antypas, J. S. Escher, J. Edgecumbe, and R. S. Enck., “Broadband GaAs transmission photocathode,” J. Appl. Phys. 49(7), 4301 (1978).
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Escher, J. S.

G. A. Antypas, J. S. Escher, J. Edgecumbe, and R. S. Enck., “Broadband GaAs transmission photocathode,” J. Appl. Phys. 49(7), 4301 (1978).
[Crossref]

Esposito, T.

S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
[Crossref]

Feng, C.

C. Feng, Y. J. Zhang, Y. S. Qian, F. Shi, J. J. Zou, and Y. G. Zeng, “Photoemission characteristics of thin GaAs-based heterojunction photocathodes,” J. Appl. Phys. 117(2), 023103 (2015).
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C. Feng, Y. J. Zhang, and Y. S. Qian, “Theoretical revision of quantum efficiency formula for thin AlGaAs/GaAs photocathodes,” Proc. SPIE 9270, 92701F (2014).

Fudurich, R. L.

J. A. Hutchby and R. L. Fudurich, “Theoretical optimization and parametric study of n-on-p AlxGal-xAs-GaAs graded band-gap solar cell,” J. Appl. Phys. 47(7), 3152–3158 (1976).
[Crossref]

Fujii, Y.

S. Moré, S. Tanaka, S. Tanaka, Y. Fujii, and M. Kamada, “Interaction of Cs and O with GaAs (100) at the overlayer–substrate interface during negative electron affinity type activations,” Surf. Sci. 527(1–3), 41–50 (2003).
[Crossref]

Garwin, E. L.

T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
[Crossref]

T. Maruyama, E. L. Garwin, R. A. Mair, R. Prepost, J. S. Smith, and J. D. Walker, “Electron-spin polarization in photoemission from thin AlxGa1-xAs,” J. Appl. Phys. 73(10), 5189 (1993).
[Crossref]

Guo, H.

Hao, G.

Harkay, K.

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
[Crossref]

Harris, J. S.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

Hernandez-Garcia, C.

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
[Crossref]

Hill, G.

I. M. Dharmadasa, J. S. Roberts, and G. Hill, “Third generation multi-layer graded band gap solar cells for achieving high conversion efficiencies—II: Experimental results,” Sol. Energy Mater. Sol. Cells 88(4), 413–422 (2005).
[Crossref]

Horinaka, H.

W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
[Crossref]

Howe, R. T.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
[Crossref]

Hutchby, J. A.

J. A. Hutchby and R. L. Fudurich, “Theoretical optimization and parametric study of n-on-p AlxGal-xAs-GaAs graded band-gap solar cell,” J. Appl. Phys. 47(7), 3152–3158 (1976).
[Crossref]

James, L. W.

G. A. Antypas, L. W. James, and J. J. Uebbing, “Operation of III-V semiconductor photocathodes in the semitransparent mode,” J. Appl. Phys. 41(7), 2888–2894 (1970).
[Crossref]

Jean, J.

K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
[Crossref]

Jones, L. B.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

Kamada, M.

S. Moré, S. Tanaka, S. Tanaka, Y. Fujii, and M. Kamada, “Interaction of Cs and O with GaAs (100) at the overlayer–substrate interface during negative electron affinity type activations,” Surf. Sci. 527(1–3), 41–50 (2003).
[Crossref]

Karkare, S.

S. Karkare, L. Boulet, L. Cultrera, B. Dunham, X. Liu, W. Schaff, and I. Bazarov, “Ultrabright and ultrafast III-V semiconductor photocathodes,” Phys. Rev. Lett. 112(9), 097601 (2014).
[Crossref] [PubMed]

S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
[Crossref]

Kato, T.

W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
[Crossref]

Kelso, S. M.

D. E. Aspnes, S. M. Kelso, R. A. Logan, and R. Bhat, “Optical properties of AlxGa1-xAs,” J. Appl. Phys. 60(2), 754–767 (1986).
[Crossref]

Kim, B.

M. Kwon, I. Park, J. Kim, J. Kim, B. Kim, and S. Park, “Gradient doping of Mg in p-type GaN for high efficiency InGaN–GaN ultraviolet light-emitting diode,” IEEE Photonics Technol. Lett. 19(23), 1880–1882 (2007).
[Crossref]

Kim, J.

M. Kwon, I. Park, J. Kim, J. Kim, B. Kim, and S. Park, “Gradient doping of Mg in p-type GaN for high efficiency InGaN–GaN ultraviolet light-emitting diode,” IEEE Photonics Technol. Lett. 19(23), 1880–1882 (2007).
[Crossref]

M. Kwon, I. Park, J. Kim, J. Kim, B. Kim, and S. Park, “Gradient doping of Mg in p-type GaN for high efficiency InGaN–GaN ultraviolet light-emitting diode,” IEEE Photonics Technol. Lett. 19(23), 1880–1882 (2007).
[Crossref]

Kirby, R. E.

T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
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Konagai, M.

M. Konagai and K. Takahashi, “Theoretical analysis of graded-band-gap gallium-aluminum arsenide/gallium arsenide solar cells,” Solid-State Electron. 19(3), 259–264 (1976).
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Kosolobov, S. N.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

Kwon, M.

M. Kwon, I. Park, J. Kim, J. Kim, B. Kim, and S. Park, “Gradient doping of Mg in p-type GaN for high efficiency InGaN–GaN ultraviolet light-emitting diode,” IEEE Photonics Technol. Lett. 19(23), 1880–1882 (2007).
[Crossref]

Legg, R.

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
[Crossref]

Liu, X.

S. Karkare, L. Boulet, L. Cultrera, B. Dunham, X. Liu, W. Schaff, and I. Bazarov, “Ultrabright and ultrafast III-V semiconductor photocathodes,” Phys. Rev. Lett. 112(9), 097601 (2014).
[Crossref] [PubMed]

Liu, X. H.

S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
[Crossref]

Liuti, S.

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

Logan, R. A.

D. E. Aspnes, S. M. Kelso, R. A. Logan, and R. Bhat, “Optical properties of AlxGa1-xAs,” J. Appl. Phys. 60(2), 754–767 (1986).
[Crossref]

Luh, D.-A.

T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
[Crossref]

MacMillan, H. F.

K. A. Costello, V. W. Aebi, and H. F. MacMillan, “Imaging GaAs vacuum photodiode with 40% quantum efficiency at 530 nm,” Proc. SPIE 1243, 99–106 (1990).
[Crossref]

Mair, R. A.

T. Maruyama, E. L. Garwin, R. A. Mair, R. Prepost, J. S. Smith, and J. D. Walker, “Electron-spin polarization in photoemission from thin AlxGa1-xAs,” J. Appl. Phys. 73(10), 5189 (1993).
[Crossref]

Maruyama, T.

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
[Crossref]

T. Maruyama, E. L. Garwin, R. A. Mair, R. Prepost, J. S. Smith, and J. D. Walker, “Electron-spin polarization in photoemission from thin AlxGa1-xAs,” J. Appl. Phys. 73(10), 5189 (1993).
[Crossref]

Matsuyama, T.

W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
[Crossref]

Melosh, N. A.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
[Crossref]

Militsyn, B. L.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

Moré, S.

S. Moré, S. Tanaka, S. Tanaka, Y. Fujii, and M. Kamada, “Interaction of Cs and O with GaAs (100) at the overlayer–substrate interface during negative electron affinity type activations,” Surf. Sci. 527(1–3), 41–50 (2003).
[Crossref]

Moy, A.

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

Nakanishi, T.

W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
[Crossref]

Narasimhan, V. K.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
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Niu, J.

Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
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Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
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Y. J. Zhang, J. Niu, J. Zhao, J. J. Zou, B. K. Chang, F. Shi, and H. C. Cheng, “Influence of exponential-doping structure on photoemission capability of transmission-mode GaAs photocathodes,” J. Appl. Phys. 108(9), 093108 (2010).
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Y. Zhang, J. Niu, J. Zou, B. Chang, and Y. Xiong, “Variation of spectral response for exponential-doped transmission-mode GaAs photocathodes in the preparation process,” Appl. Opt. 49(20), 3935–3940 (2010).
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Y. Zhang, B. Chang, Z. Yang, J. Niu, Y. Xiong, F. Shi, H. Guo, and Y. Zeng, “Annealing study of carrier concentration in gradient-doped GaAs/GaAlAs epilayers grown by molecular beam epitaxy,” Appl. Opt. 48(9), 1715–1720 (2009).
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Okumi, S.

W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
[Crossref]

Padmore, H.

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
[Crossref]

Park, I.

M. Kwon, I. Park, J. Kim, J. Kim, B. Kim, and S. Park, “Gradient doping of Mg in p-type GaN for high efficiency InGaN–GaN ultraviolet light-emitting diode,” IEEE Photonics Technol. Lett. 19(23), 1880–1882 (2007).
[Crossref]

Park, S.

M. Kwon, I. Park, J. Kim, J. Kim, B. Kim, and S. Park, “Gradient doping of Mg in p-type GaN for high efficiency InGaN–GaN ultraviolet light-emitting diode,” IEEE Photonics Technol. Lett. 19(23), 1880–1882 (2007).
[Crossref]

Poelker, M.

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

Prepost, R.

T. Maruyama, A. Brachmann, J. E. Clendenin, T. Desikan, E. L. Garwin, R. E. Kirby, D.-A. Luh, J. Turner, and R. Prepost, “A very high charge, high polarization gradient-doped strained GaAs photocathode,” Nucl. Instrum. Methods Phys. Res. A 492(1-2), 199–211 (2002).
[Crossref]

T. Maruyama, E. L. Garwin, R. A. Mair, R. Prepost, J. S. Smith, and J. D. Walker, “Electron-spin polarization in photoemission from thin AlxGa1-xAs,” J. Appl. Phys. 73(10), 5189 (1993).
[Crossref]

Prok, Y.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

Qian, Y. S.

C. Feng, Y. J. Zhang, Y. S. Qian, F. Shi, J. J. Zou, and Y. G. Zeng, “Photoemission characteristics of thin GaAs-based heterojunction photocathodes,” J. Appl. Phys. 117(2), 023103 (2015).
[Crossref]

C. Feng, Y. J. Zhang, and Y. S. Qian, “Theoretical revision of quantum efficiency formula for thin AlGaAs/GaAs photocathodes,” Proc. SPIE 9270, 92701F (2014).

Rao, T.

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
[Crossref]

Ren, B.

Riley, D. C.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
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I. M. Dharmadasa, J. S. Roberts, and G. Hill, “Third generation multi-layer graded band gap solar cells for achieving high conversion efficiencies—II: Experimental results,” Sol. Energy Mater. Sol. Cells 88(4), 413–422 (2005).
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Rosenthal, S. J.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

Rozhkov, S. A.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

Sahasrabuddhe, K.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
[Crossref]

Saka, T.

W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
[Crossref]

Sarmiento, T.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

Sawyer, E.

S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
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Schaff, W.

S. Karkare, L. Boulet, L. Cultrera, B. Dunham, X. Liu, W. Schaff, and I. Bazarov, “Ultrabright and ultrafast III-V semiconductor photocathodes,” Phys. Rev. Lett. 112(9), 097601 (2014).
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S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
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Scheibler, H. E.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

Schmitt, F.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

Schwede, J. W.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
[Crossref]

Sell, D. D.

H. C. Casey, D. D. Sell, and K. W. Wecht, “Concentration dependence of the absorption coefficient for n− and p−type GaAs between 1.3 and 1.6 eV,” J. Appl. Phys. 46(1), 250–257 (1975).
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Shen, Z. X.

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
[Crossref] [PubMed]

K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
[Crossref]

Shi, F.

C. Feng, Y. J. Zhang, Y. S. Qian, F. Shi, J. J. Zou, and Y. G. Zeng, “Photoemission characteristics of thin GaAs-based heterojunction photocathodes,” J. Appl. Phys. 117(2), 023103 (2015).
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G. Hao, F. Shi, H. Cheng, B. Ren, and B. Chang, “Photoemission performance of thin graded structure AlGaN photocathode,” Appl. Opt. 54(10), 2572–2576 (2015).
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Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
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Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
[Crossref]

Y. J. Zhang, J. Niu, J. Zhao, J. J. Zou, B. K. Chang, F. Shi, and H. C. Cheng, “Influence of exponential-doping structure on photoemission capability of transmission-mode GaAs photocathodes,” J. Appl. Phys. 108(9), 093108 (2010).
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Y. Zhang, B. Chang, Z. Yang, J. Niu, Y. Xiong, F. Shi, H. Guo, and Y. Zeng, “Annealing study of carrier concentration in gradient-doped GaAs/GaAlAs epilayers grown by molecular beam epitaxy,” Appl. Opt. 48(9), 1715–1720 (2009).
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D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
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Smith, J. S.

T. Maruyama, E. L. Garwin, R. A. Mair, R. Prepost, J. S. Smith, and J. D. Walker, “Electron-spin polarization in photoemission from thin AlxGa1-xAs,” J. Appl. Phys. 73(10), 5189 (1993).
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Smith, S. L.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
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Y. Yang, W. Z. Yang, and C. D. Sun, “Heterostructured cathode with graded bandgap window-layer for photon-enhanced thermionic emission solar energy converters,” Sol. Energy Mater. Sol. Cells 132, 410–417 (2015).
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Terekhov, A. S.

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
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G. A. Antypas, L. W. James, and J. J. Uebbing, “Operation of III-V semiconductor photocathodes in the semitransparent mode,” J. Appl. Phys. 41(7), 2888–2894 (1970).
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J. Wehmeijer and B. van Geest, “High-speed imaging: Image intensification,” Nat. Photonics 4(3), 152–153 (2010).
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Wada, K.

W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
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Walker, J. D.

T. Maruyama, E. L. Garwin, R. A. Mair, R. Prepost, J. S. Smith, and J. D. Walker, “Electron-spin polarization in photoemission from thin AlxGa1-xAs,” J. Appl. Phys. 73(10), 5189 (1993).
[Crossref]

Wan, W.

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
[Crossref]

Wecht, K. W.

H. C. Casey, D. D. Sell, and K. W. Wecht, “Concentration dependence of the absorption coefficient for n− and p−type GaAs between 1.3 and 1.6 eV,” J. Appl. Phys. 46(1), 250–257 (1975).
[Crossref]

Wehmeijer, J.

J. Wehmeijer and B. van Geest, “High-speed imaging: Image intensification,” Nat. Photonics 4(3), 152–153 (2010).
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Xiong, Y.

Xu, Y.

Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
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Yang, W. Z.

Y. Yang, W. Z. Yang, and C. D. Sun, “Heterostructured cathode with graded bandgap window-layer for photon-enhanced thermionic emission solar energy converters,” Sol. Energy Mater. Sol. Cells 132, 410–417 (2015).
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Yang, Y.

Y. Yang, W. Z. Yang, and C. D. Sun, “Heterostructured cathode with graded bandgap window-layer for photon-enhanced thermionic emission solar energy converters,” Sol. Energy Mater. Sol. Cells 132, 410–417 (2015).
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Yang, Z.

Zeng, Y.

Zeng, Y. G.

C. Feng, Y. J. Zhang, Y. S. Qian, F. Shi, J. J. Zou, and Y. G. Zeng, “Photoemission characteristics of thin GaAs-based heterojunction photocathodes,” J. Appl. Phys. 117(2), 023103 (2015).
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Zhang, Y.

Zhang, Y. J.

C. Feng, Y. J. Zhang, Y. S. Qian, F. Shi, J. J. Zou, and Y. G. Zeng, “Photoemission characteristics of thin GaAs-based heterojunction photocathodes,” J. Appl. Phys. 117(2), 023103 (2015).
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Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
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C. Feng, Y. J. Zhang, and Y. S. Qian, “Theoretical revision of quantum efficiency formula for thin AlGaAs/GaAs photocathodes,” Proc. SPIE 9270, 92701F (2014).

Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
[Crossref]

Y. J. Zhang, J. Niu, J. Zhao, J. J. Zou, B. K. Chang, F. Shi, and H. C. Cheng, “Influence of exponential-doping structure on photoemission capability of transmission-mode GaAs photocathodes,” J. Appl. Phys. 108(9), 093108 (2010).
[Crossref]

Zhao, J.

Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
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Y. J. Zhang, J. Niu, J. Zhao, J. J. Zou, B. K. Chang, F. Shi, and H. C. Cheng, “Influence of exponential-doping structure on photoemission capability of transmission-mode GaAs photocathodes,” J. Appl. Phys. 108(9), 093108 (2010).
[Crossref]

Zhen, W.

W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
[Crossref]

Zheng, X.

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
[Crossref]

Zhou, F.

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
[Crossref]

Zou, J.

Zou, J. J.

C. Feng, Y. J. Zhang, Y. S. Qian, F. Shi, J. J. Zou, and Y. G. Zeng, “Photoemission characteristics of thin GaAs-based heterojunction photocathodes,” J. Appl. Phys. 117(2), 023103 (2015).
[Crossref]

Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
[Crossref]

Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
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Y. J. Zhang, J. Niu, J. Zhao, J. J. Zou, B. K. Chang, F. Shi, and H. C. Cheng, “Influence of exponential-doping structure on photoemission capability of transmission-mode GaAs photocathodes,” J. Appl. Phys. 108(9), 093108 (2010).
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AIP Conf. Proc. (2)

A. Moy, T. Maruyama, F. Zhou, A. Brachmann, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “MBE growth of graded structures for polarized electron emitters,” AIP Conf. Proc. 1149(1), 1038–1046 (2009).
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L. B. Jones, S. A. Rozhkov, V. V. Bakin, S. N. Kosolobov, B. L. Militsyn, H. E. Scheibler, S. L. Smith, A. S. Terekhov, D. G. Crabb, Y. Prok, M. Poelker, S. Liuti, D. B. Day, and X. Zheng, “Cooled transmission–mode NEA–photocathode with a band–graded active layer for high brightness electron source,” AIP Conf. Proc. 1149(1), 1057–1061 (2009).
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Appl. Opt. (3)

Appl. Phys. Lett. (1)

Y. J. Zhang, B. K. Chang, J. Niu, J. Zhao, J. J. Zou, F. Shi, and H. C. Cheng, “High-efficiency graded band-gap AlxGa1-xAs/GaAs photocathodes grown by metalorganic chemical vapor deposition,” Appl. Phys. Lett. 99(10), 101104 (2011).
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IEEE Photonics Technol. Lett. (1)

M. Kwon, I. Park, J. Kim, J. Kim, B. Kim, and S. Park, “Gradient doping of Mg in p-type GaN for high efficiency InGaN–GaN ultraviolet light-emitting diode,” IEEE Photonics Technol. Lett. 19(23), 1880–1882 (2007).
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S. Karkare, D. Dimitrov, W. Schaff, L. Cultrera, A. Bartnik, X. H. Liu, E. Sawyer, T. Esposito, and I. Bazarov, “Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes,” J. Appl. Phys. 113(10), 104904 (2013).
[Crossref]

K. Sahasrabuddhe, J. W. Schwede, I. Bargatin, J. Jean, R. T. Howe, Z. X. Shen, and N. A. Melosh, “A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission,” J. Appl. Phys. 112(9), 094907 (2012).
[Crossref]

T. Maruyama, E. L. Garwin, R. A. Mair, R. Prepost, J. S. Smith, and J. D. Walker, “Electron-spin polarization in photoemission from thin AlxGa1-xAs,” J. Appl. Phys. 73(10), 5189 (1993).
[Crossref]

C. Feng, Y. J. Zhang, Y. S. Qian, F. Shi, J. J. Zou, and Y. G. Zeng, “Photoemission characteristics of thin GaAs-based heterojunction photocathodes,” J. Appl. Phys. 117(2), 023103 (2015).
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W. Zhen, T. Matsuyama, H. Horinaka, K. Wada, T. Nakanishi, S. Okumi, T. Kato, and T. Saka, “Spin relaxation of electrons in graded doping strained GaAs-layer photocathode of polarized electron source,” Jpn. J. Appl. Phys. 38(Part 2, No. 1A/B), L41–L43 (1999).
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Nat. Commun. (1)

J. W. Schwede, T. Sarmiento, V. K. Narasimhan, S. J. Rosenthal, D. C. Riley, F. Schmitt, I. Bargatin, K. Sahasrabuddhe, R. T. Howe, J. S. Harris, N. A. Melosh, and Z. X. Shen, “Photon-enhanced thermionic emission from heterostructures with low interface recombination,” Nat. Commun. 4, 1576 (2013).
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Nat. Photonics (1)

J. Wehmeijer and B. van Geest, “High-speed imaging: Image intensification,” Nat. Photonics 4(3), 152–153 (2010).
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Nucl. Instrum. Methods Phys. Res. A (2)

D. H. Dowell, I. Bazarov, B. Dunham, K. Harkay, C. Hernandez-Garcia, R. Legg, H. Padmore, T. Rao, J. Smedley, and W. Wan, “Cathode R&D for future light sources,” Nucl. Instrum. Methods Phys. Res. A 622(3), 685–697 (2010).
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[Crossref]

Opt. Commun. (1)

Y. J. Zhang, J. Niu, J. J. Zou, X. L. Chen, Y. Xu, B. K. Chang, and F. Shi, “Surface activation behavior of negative-electron-affinity exponential-doping GaAs photocathodes,” Opt. Commun. 321, 32–37 (2014).
[Crossref]

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[Crossref] [PubMed]

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C. Feng, Y. J. Zhang, and Y. S. Qian, “Theoretical revision of quantum efficiency formula for thin AlGaAs/GaAs photocathodes,” Proc. SPIE 9270, 92701F (2014).

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[Crossref]

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[Crossref]

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Figures (6)

Fig. 1
Fig. 1 Energy band structure diagram of the graded bandgap AlxGa1-xAs/GaAs heterojunction photocathode. Ec is the conduction-band minimum, Ev is the valence band maximum, Eg is the bandgap, EF is the Fermi level, E 0 is the vacuum level.

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Fig. 2
Fig. 2 Theoretical quantum efficiency curves with the change of T e for AlxGa1-xAs/GaAs photocathodes operating in the (a) r-mode and (b) t-mode, respectively.

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Fig. 3
Fig. 3 Theoretical quantum efficiency curves with the change of T w for AlxGa1-xAs/GaAs photocathodes operating in the (a) r-mode and (b) t-mode, respectively.

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Fig. 4
Fig. 4 Theoretical quantum efficiency curves with different Al proportion distribution for AlxGa1-xAs/GaAs photocathodes operating in the (a) r-mode and (b) t-mode, respectively.

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Fig. 5
Fig. 5 Experimental quantum efficiency curve of the r-mode AlxGa1-xAs/GaAs sample and the fitted curve via the deduced model.

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Fig. 6
Fig. 6 Experimental quantum efficiency curve of the t-mode AlxGa1-xAs/GaAs sample and the fitted curve via the deduced model.

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Tables (1)

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Table 1 Fitted performance parameters of the quantum efficiency curves

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Equations (17)

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D n i d 2 n i ( x ) d x 2 + μ i | E | d n i ( x ) d x − n i ( x ) τ i + g i ( x ) = 0 , i = 1 , 2 , 3 , … , n
g i ( x ) = ( 1 − R h v ) I 0 α h v i exp ( − α h v 0 T e ) exp [ − α h v i ( x − T e ) ] , i = 1
g i ( x ) = ( 1 − R h v ) I 0 α h v i exp ( − α h v 0 T e ) [ ∏ m = 1 i − 1 exp ( − α h v m T w m ) ] exp [ − α h v i ( x − T d i − 1 ) ] ,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     i = 2 , 3 , … , n
g i ( x ) = ( 1 − R h v ) I 0 α h v i [ ∏ m = i + 1 n exp ( − α h v m T w m ) ] exp [ − α h v i ( T d i − x ) ] , i = 1 , 2 , … , n − 1
g i ( x ) = ( 1 − R h v ) I 0 α h v i exp [ − α h v i ( T d i − x ) ] , i = n
D n i = { 200 − 550 x + 250 x 2 ( cm 2 /s ) , 0 < x < 0.45 − 6.4 + 29 x − 18 x 2 ( cm 2 /s ) , 0.45 < x < 1
μ i = { 8000 − 22000 x + 10000 x 2 ( cm 2 V − 1 s − 1 ) , 0 < x < 0.45 − 255 + 1160 x − 720 x 2 ( cm 2 V − 1 s − 1 ) , 0.45 < x < 1
E = E g n − E g 1 T d n − T e
E g ( x ) = 1.424 + 1.594 x + x ( 1 − x ) ( 0.127 − 1.310 x )
[ D n i d n i ( x ) d x + μ i | E | n i ( x ) ] | x = T d i = − S v i + 1 n i ( x ) | x = T d i + S v i + 1 n i + 1 ( x ) | x = T d i
[ D n i d n i ( x ) d x + μ i | E | n i ( x ) ] | x = T d i − 1 = S v i n i ( x ) | x = T d i − 1
n i ( x ) | x = T e + T w = 0
[ D n i d n i ( x ) d x + μ i | E | n i ( x ) ] | x = T d i − 1 = S v i n i ( x ) | x = T d i − 1
D n 0 d 2 n 0 ( x ) d x 2 + μ 0 | E 0 | d n 0 ( x ) d x − n 0 ( x ) τ 0 + ( 1 − R h v ) I 0 α h v 0 exp ( − α h v 0 x ) = 0 , x ∈ [ 0 , T e ]
D n 0 d 2 n 0 ( x ) d x 2 + μ 0 | E 0 | d n 0 ( x ) d x − n 0 ( x ) τ 0 + ( 1 − R h v ) I 0 α h v 0 [ ∏ m = 1 n exp ( − α h v m T w m ) ]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   × exp [ − α h v 0 ( T e − x ) ] = 0 ,                 x ∈ [ 0 , T e ]
n 0 ( x ) | x = 0 = 0
[ D n 0 d n 0 ( x ) d x + μ 0 | E 0 | n 0 ( x ) ] | x = T e = − S v 1 n 0 ( x ) | x = T e + S v 1 n 1 ( x ) | x = T e

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