In this study, a thermal and electrical coupled device solver is developed to simulate the energy transfer mechanism within a GaN FET with a gate length of 0.2 μm. The simulation simultaneously solves a set of hydrodynamic equations (derived from the Boltzmann Transport Equation) and the Poisson equation for electron, optical phonon and acoustic phonon energies, electron number density, electric field and electric potential. This approach has been previously established for gallium arsenide (GaAs) devices [36,37], but has not been extended to GaN due to the lack of readily available property values for GaN devices that are required. Via extensive literature study, high-fidelity properties for GaN were collected in analytical forms with respect to many dependencies, e.g. lattice temperature, electrical field, electron number density, doping rate, defects rate. These properties are then implemented into the developed code to provide a high accuracy sub-micron GaN device simulation.
Simulations show that non-equilibrium heat generation is exhibited in a typical device while the drain current is reduced due to the decrease in electron mobility. Future analysis is needed to quantify the hot-electron effect on reducing the drain current and to discover more effective ways of heat removal.