Nonlinear Polarization and Efficiency Droop in Hexagonal InGaN/GaN Disk-in-Wire LEDs

Abstract

Recent studies suggest that piezoelectric polarization can play an important role in determining the electronic and optical properties of nanoscale nitride heterostructures. Among a few models available, recent first-principles calculations performed by Prodhomme et al. provide a simple yet accurate description of linear and nonlinear piezoelectric coefficients in reduced dimensionality structures having wurtzite crystal symmetry. In this paper, first, within a fully atomistic VFF-sp3s* tight-binding framework, we employ the model proposed by Prodhomme et al. to evaluate the importance of nonlinear piezoelectricity on the single-particle electronic states and interband optical transitions in a recently reported hexagon shaped In0.25Ga0.75N/GaN disk-in-wire LED. The microscopically determined transition parameters are then incorporated into a TCAD toolkit to investigate how atomicity and the net polarization field affect the internal quantum efficiency of the LED and lead to a degraded efficiency droop characteristic