MONTE-CARLO SIMULATION OF A GAAS ELECTRON SOURCE

Photoelectron transport in a GaAs electron source was studied using a Monte Carlo simulation technique. The principle of the method is to simulate the motion of photoexcited hot electrons in GaAs real space, taking into account various scattering mechanisms. The calculated electron energy distribution is in very good agreement with experimental measurements. The calculation predicts the electron emittance at the GaAs surface being from 2.70 pi to 3.29 pi mm mrad and the electron transit time spread (TTS) of the source ranging from 270 to 284 ps. It was also found that the hot photoelectron mean free path is 117.5 to 39.4 nm with the incident photon energy changing from 1.6 to 2.5 eV.