High-energy electron relaxation and full-band electron dynamics in aluminium nitride

Abstract

Material properties of AlN, particularly its wide band gap around 6 eV, warrant its operation in the high-field transport regimes reaching MV/cm fields. In this theoretical work, we examine the full-band scattering of conduction band electrons in AlN due to polar optical phonon (POP) emission, which is the main scattering channel at high fields. First, we obtain the band structure for the wurtzite phase of AlN using the empirical pseudopotential method. Scattering rates along the full length of several high-symmetry directions are computed efficiently through the Lehmann-Taut Brillouin zone integration technique. In order to shed light on the behaviour of the velocity-field characteristics at extremely high electric fields, in the order of a few MV/cm, we resort to an Esaki-Tsu estimation. Comparison of these results for AlN is made with our similar work on GaN. With typically more than 50% higher POP scattering rate compared to GaN, AlN has poorer high-field prospects. Availability of these data for AlN and GaN paves the way for practical assessment of the high-energy electron dynamics for the ternary alloy, AlGaN.