First-Principles Investigations of Defects and Surfaces and Their Impact on Nitride Devices

摘要

This project was aimed at elucidating the electronic structure of nitride semiconductor surfaces, defects, and impurities through first- principles calculations. Density functional theory is the standard approach, but in its routine implementation it has major deficiencies because the band gap of semiconductors is severely underestimated. A new approach based on 'hybrid functionals' was used to overcome this problem. Two main topics were pursued. (1) Behavior of fluorine in nitride semiconductors. A through understanding of the behavior of interstitial flooring were developed. It was proposed that flouring deceptors may be useful for p-type doping of wide-band- gap semiconductors. (2) Effects of surfaces on the two-dimensional electron gas. It was determined that oxidized surfac3es, which represent the realistic condition of the surface are most relevant.