Comparison of GaAs photocathode grown by MOCVD and MBE: a first-principle and experimental research

Abstract

Negative electron affinity GaAs photocathode is made from p-type doped photocathode, and the p-type GaAs photocathode is commonly doped by Be or Zn atoms. To investigate the doping differences of the two dopants, the undoped GaAs(100)β2(2 × 4) reconstruction surface model and doped models with Zn or Be doping at position I, II, III, IV, V are built, and the related performance parameters are calculated and compared. The first-principle method is used to calculate the geometric structure, formation energy, band structure, density of state, work function and Mulliken population of the surface models, it is found that Be is more suitable for forming interstitial doping and Zn is better to form substitution doping, and position II is the best doping position for Zn substitution doping. Then the experiment is carried on the two doped GaAs photocathodes grown by MBE and MOCVD, the experimental result shows the Zn-doped GaAs photocathode grown by MOCVD has better spectral response and quantum efficiency, which verifies the correctness of theoretical result.