Quantum efficiency of heterostructured AlN/AlxGa1−xN photocathodes with graded bandgap emission layer

  • Mingzhu Yang
  • Jing Guo
  • Xiaoqian Fu
  • Zhanhui Liu


A heterostructured AlN/AlxGa1−xN photocathode consisting of a sapphire substrate layer, a AlN buffer layer, and a graded bandgap emission layer is proposed to improve the quantum efficiency of AlGaN photocathode. The theoretical models for transmission-mode and reflection-mode photocathodes were deduced based on one-dimensional continuity equations to analyze the characteristics of the devices. Results show that the multilevel built-in electric field induced by the bandgap gradation in the emission layer can improve the quantum efficiency because of the longer electron diffusion length and the reduction of the back-interface recombination losses. The effect of thicknesses of photocathodes and Al composition in the sublayers on efficiency is discussed. This work would provide theoretical guidance for better performance of AlGaN photocathodes.



This work is financed by the National Natural Science Foundation of China (Grant No. 61705108), the Natural Science Foundation of Jiangsu Province (Grant No. BK20170959), and the startup foundation for introducing talent of NUIST (Grant No. 2016r039). It is also financed by the National Natural Science Foundation of China (Grant Nos. 61704075 and 61601198).


  1. 1.
    J. Wu, X. Han, J. Li, H. Wei, G. Cong, X. Liu, Q. Zhu, Z. Wang, Q. Jia, Liping Guo, Tiandou Hu, Huanhua Wang, Crack control in GaN grown on silicon (111) using In doped low-temperature AlGaN interlayer by metalorganic chemical vapor deposition. Opt. Mater. 28, 1227–1231 (2006)CrossRefGoogle Scholar
  2. 2.
    G. Wang, F. Xie, H. Lua, D. Chen, R. Zhang, Y. Zheng, Performance comparison of front- and back-illuminated AlGaN-based metal–semiconductor–metal solar-blind ultraviolet photodetectors. J. Vac. Sci. Technol. B 31, 011202 (2013)CrossRefGoogle Scholar
  3. 3.
    M. Yang, B. Chang, W. Rao, Relationship of the longer wavelength threshold and the narrower surface band gap: for GaN and GaAlN photocathodes. Optik 127, 10710–10715 (2016)CrossRefGoogle Scholar
  4. 4.
    X. Wang, B. Chang, Y. Du, J. Qiao, Quantum efficiency of GaN photocathode under different illumination. Appl. Phys. Lett. 99, 042102 (2011)CrossRefGoogle Scholar
  5. 5.
    M. Sumiya, Y. Kamo, N. Ohashi, M. Takeguchi, Y.U. Heo, H. Yoshikawa, S. Ueda, K. Kobayashi, T. Nihashi, M. Hagino, Others, Fabrication and hard X-ray photoemission analysis of photocathodes with sharp solar-blind sensitivity using AlGaN films grown on Si substrates. Appl. Surf. Sci. 256, 4442–4446 (2010)CrossRefGoogle Scholar
  6. 6.
    J.L. Reverchon, G. Mazzeo, A. Dussaigne, J.Y. Duboz, Status of AlGaN based focal plane arrays for UV solar blind detection. Proc. SPIE 5964, 596420 (2005)Google Scholar
  7. 7.
    M.R. Ainbund, A.N. Alekseev, O.V. Alymov, V.N. Jmerik, L.V. Lapushkina, A.M. Mizerov, S.V. Ivanov, A.V. Pashuk, S.I. Petrov, Solar-blind UV photocathodes based on AlGaN heterostructures with a 300- to 330- nm spectral sensitivity threshold. Tech. Phys. Lett. 5, 439–442 (2012)CrossRefGoogle Scholar
  8. 8.
    Y. Zhang, J. Zou, J. Niu, J. Zhao, B. Chang, Photoemission characteristics of different-structure reflection-mode GaAs photocathodes. J. Appl. Phys. 110, 063113 (2011)CrossRefGoogle Scholar
  9. 9.
    X. Chen, G. Hao, B. Chang, Y. Zhang, J. Zhao, Y. Xu, M. Jin, Stability of negative electron affinity Ga0.37Al0.63As photocathodes in an ultrahigh vacuum system. Appl. Opt. 52, 6272–6277 (2013)CrossRefGoogle Scholar
  10. 10.
    X. Wang, B.C.L. Ren, P. Gao, Influence of the p-type doping concentration on reflection-mode GaN photocathode. Appl. Phys. Lett. 98, 082109 (2011)CrossRefGoogle Scholar
  11. 11.
    J. Li, T.N. Oder, M.L. Nakarmi, J.Y. Lin, H.X. Jiang, Optical and electrical properties of Mg-doped p-type AlxGa1–xN. Appl. Phys. Lett. 80, 1210–1212 (2002)CrossRefGoogle Scholar
  12. 12.
    P. Kozodoy, M. Hansen, S.P. DenBaars, U.K. Mishra, Enhanced Mg doping efficiency in Al0.2Ga0.8N/GaN superlattices. Appl. Phys. Lett. 74, 3681–3683 (1999)CrossRefGoogle Scholar
  13. 13.
    M. Yang, B. Chang, G. Hao, F. Shi, H. Wang, M. Wang, Research on electronic structure and optical properties of Mg doped Ga0.75Al0.25N. Opt. Mater. 36, 787–796 (2014)CrossRefGoogle Scholar
  14. 14.
    W.E. Spicer, A. Herrera-Gõmez, Modern theory and applications of photocathodes, Proc. SPIE, 2022, 18 (1993)CrossRefGoogle Scholar
  15. 15.
    G.A. Antypas, L.W. James, J.J. Uebbing, Operation of III-V semiconductor photocathodes in the semitransparent mode. J. Appl. Phys. 41, 2888–2894 (1970)CrossRefGoogle Scholar
  16. 16.
    Y. Koide, H. Itoh, M.R.H. Khan, K. Hiramato, N. Sawaki, I. Akasaki, J. Appl. Phys. 61, 4540 (1987)CrossRefGoogle Scholar
  17. 17.
    J.J. Zou, B.K. Chang, H.L. .Chen, L. Liu, Variation of quantumyield curves for GaAs photocathodes under illumination. J. Appl. Phys. 101, 033126 (2007)CrossRefGoogle Scholar
  18. 18.
    J.F. Muth, J.D. Brown, M.A.L. Johnson, Z.H. Yu, R.M. Kolbas, J.W. Cook, J.F. Schetzina, Absorption coefficient and refractive index of GaN, AlN, and AlGaN alloys. MRS Internet J. Nitride Semicond. Res. 4(S1), G5.2 (1999)CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Mingzhu Yang
    • 1
  • Jing Guo
    • 2
  • Xiaoqian Fu
    • 3
  • Zhanhui Liu
    • 1
  1. 1.School of Physics and Optoelectronic EngineeringNanjing University of Information Science and TechnologyNanjingChina
  2. 2.School of AutomationNanjing Institute of TechnologyNanjingChina
  3. 3.School of Information Science and EngineeringUniversity of JinanJinanChina

Personalised recommendations