High field transport studies of GaN

We report on experimental and theoretical studies of high field transport in bulk GaN. Theoretically, we have investigated the electron-phonon interaction in this material based on empirical pseudopotential method (EPM) calculations for the bandstructure, together with an empirical valence shell model for the lattice dynamics in cubic GaN. The rigid-ion model is used to calculate the electron-phonon scattering rate for all modes, and to extract a deformation potential for use in high field transport calculations. A full band Monte-Carlo (FBMC) method is used to simulate high field transport in GaN. In the experimental studies, we have fabricated etched constrictions for performing pulse I-V measurements in bulk GaN and GaN/AlGaN heterostructures. The experimentally extracted velocity-field characteristics are in good agreement with transport calculations up to fields as high as 1.5 × 10⁵ V/cm, where velocities up to 2.5 × 10⁷ cm/s are measured.