Insight into the photoelectron angular dependent energy distribution of negative-electron-affinity InP photocathodes

Energy distribution and angular distribution of the photoelectrons from InP photocathodes are investigated using a precise Monte Carlo model. It is found that Gamma-valley electrons contribute to the first peak of the energy distribution curve, but the second peak is contributed by both Gamma-valley and L-valley electrons rather than only L-valley electrons. L valley electrons are shown to have a smaller angular spread than Gamma-valley electrons, which is attributed to the much higher potential energy of L-valley minimum. The further simulation indicates that the performance of InP photocathodes can be improved by increasing the hole concentration or decreasing the temperature, but the activation layer thickness variation only has very slight influence on either energy or angular distribution. (C) 2014 AIP Publishing LLC.