Influences of hetero-junction buffer layers and substrates on polarity of PA-MBE grown InN films

Abstract

The polarity of InN films, grown on either GaN templates or sapphire substrates without and with various types of buffer layers using plasma-assisted molecular beam epitaxy, was investigated. From experimental results, we found that the polarity of InN films did not follow the polarity of GaN templates or GaN buffer layers and had different polarity behavior compared with PA-MBE grown GaN film. For InN films grown on Ga-polarity GaN template, they had N polarity either with or without GaN buffer layer. For InN films grown on high temperature annealed GaN buffer layer, they have In polarity due to lack of N-polarity nucleation sites. Similar results were found for InN films grown on sapphire substrates. We conclude that the polarity of InN film is independent on substrates but determined by growth nature, material characteristics of InN, and condition of heat treatment taken on buffer layers.