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

Abstract : 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.