Electron velocity distribution on the abrupt change in source–drain current of GaN devices

Abstract

An analytical model of the channel electron energy distribution in an on-state GaN transistor has been proposed based on the assumption that drift velocities of channel electrons obey the two-dimensional Maxwell–Boltzmann distribution. The validity of such an assumption was confirmed by Monte Carlo simulation. It was found that there could be a larger number of high-energy channel electrons whose energy is higher than the intervalley energy between [Formula: see text] and [Formula: see text] valleys in a GaN transistor with a high electron temperature. The fraction of hot electrons with its energy higher than the intervalley energy between [Formula: see text] and [Formula: see text] valleys to the total channel electrons can easily reach 50% when the electron temperature is higher than 3000 K. Such an electron temperature in a GaN transistor had been determined in experiments. Thus, hot electrons in the [Formula: see text] valley can transit into [Formula: see text] valleys. It suggests that intervalley transitions could be one possible physical origin of the abrupt change in the source−drain current in GaN devices. The proposed model can well explain how an abrupt change in the source–drain current in GaN transistor experiments depends on the voltage-dependent gate, the trap, etc.