Unvealing GaN Polytypism in Distributed GaN/InAlN Bragg Reflectors Through HRTEM Image Simulation

Abstract

In this work, through high resolution transmission electron microscopy (HRTEM) and image simulation, the origins of the reduced reflectivity values measured for a nearly lattice‐matched GaN/InAlN distributed Bragg reflector (DBR) are investigated. HRTEM images reveal significant structural defects in the GaN semiperiods, such as coexistence of wurtzite and zinc blende phases and zinc‐blende twinned domains, which contribute to the experimentally observed decrease in reflectivity. Contact regions arising because of the superposition of both cubic and hexagonal GaN polytypes and/or cubic twinned domains are modeled and used to simulate HRTEM images that confirm the experimental phase contrast and hence the validity of the proposed models.