Electron Momentum and Energy Relaxation Times in Wurtzite GaN, InN and AlN: A Monte Carlo Study

Abstract

Electron relaxation process and transport property of hot electrons in wurtzite GaN, InN and AlN are investigated by an ensemble Monte Carlo (EMC) method using the classic three valleys model. Both momentum and energy relaxation processes are studied here, taking into account the effect of temperature and electric field. It can be found that under different electric fields the relaxation mechanisms are much different for the existence of satellite valley structures in III-nitrides. The momentum and energy relaxation processes of InN are different from that of GaN and AlN for the much smaller effective electron mass in the lowest valley of InN. The polar optical phonon scattering is the main energy relaxation process when the electric field is lower, but inter-valley scattering will dominate the energy relaxation process when the electric field is high. The main momentum relaxation mechanisms are ionized impurity, acoustic phonon, and polar optical phonon scattering at lower electric field, but polar optical phonon and inter-valley scattering are the main momentum relaxation mechanisms when the electric field becomes higher. The momentum relaxation time is much lower than the energy relaxation time, the reason is that nearly all scattering mechanisms relax momentum, but only polar optical phonon and inter-valley scattering relax electron energy. The temperature can affect the momentum and energy relaxation by the role in scattering. Finally, the momentum and energy relaxation times as a function of electron temperature are given, which can be used for relaxation time modeling and device transport research.