Characterization of GaN thin films on HVPE GaN templates

Homoepitaxial growth of GaN thin films by RF plasma-assisted MBE on HVPE templates is examined in detail. Two different growth techniques are investigated. In one group of samples, the high-temperature GaN epitaxial layers were grown directly on HVPE-grown GaN/sapphire composite substrates. In another group of samples, intermediate temperature buffer layers (ITBLs) of 800 nm thick were first deposited on top of the HVPE GaN templates by MBE before the growth of high-temperature epitaxial GaN layers. Substantial improvements in both the photoluminescence and the Hall mobility are observed for samples grown with the use of ITBLs.