The optimal thickness of a transmission-mode GaN photocathode

• 来源期刊: 中国物理B（英文版）
• 关键词: gallium nitride transmission-mode quantum efficiency optimal thickness
• 年，卷（期）: 2012,（8）
• 页码范围: 517-521
• 页数: 5页
• 语种: 英文
• DOI: 10.1088/1674-1056/21/8/087901

摘要

A 150-nm-thick GaN photocathode with a Mg doping concentration of 1.6 × 1017 cm-3 is activated by Cs/O in an ultrahigh vacuum chamber,and a quantum efficiency (QE) curve of the negative electron affinity transmission-mode (t-mode) of the GaN photocathode is obtained.The maximum QE reaches 13.0％ at 290 nm.According to the t-mode QE equation solved from the diffusion equation,the QE curve is fitted.From the fitting results,the electron escape probability is 0.32,the back-interface recombination velocity is 5 × 104 cm·s-1,and the electron diffusion length is 116 nm.Based on these parameters,the influence of GaN thickness on t-mode QE is simulated.The simulation shows that the optimal thickness of GaN is 90 nm,which is better than the 150-nm GaN.