RETRACTED: High quantum efficiency of depth grade doping negative-electron-affinity GaN photocathode (Retracted Article)

A depth grade doping sample gallium nitride (GaN) photocathode was designed to obtain an extremely high quantum efficiency (QE). Two other uniform doping samples were prepared in the same procedure as contrast. The calibrated QE curves were achieved; by comparing theoretical calculated values with the experimental QE plots, the escape probability and diffusion length were fitted. The QE value of gradient doping sample is as high as 68.7% at 5.17 eV; the diffusion length of gradient doping sample is fitted to be 250 nm which is much higher than uniform doping samples. That explains why depth-grade-doping can improve the QE of GaN photocathode significantly. (C) 2010 American Institute of Physics. [doi:10.1063/1.3478010]