Theory of Doping and Defects in III-V Nitrides

TL;DR

This paper uses first-principles calculations to analyze doping and defect mechanisms in GaN and AlGaN alloys, revealing key factors affecting n-type and p-type conductivity and the role of various impurities.

Contribution

It provides a detailed theoretical understanding of doping challenges and defect formation in III-V nitrides, highlighting the effects of impurities and alloy composition.

Findings

Nitrogen vacancies are energetically unfavorable during growth.

Silicon and oxygen form effective donors in GaN.

Hydrogen benefits acceptor doping by reducing compensation.

Abstract

Doping problems in GaN and in AlGaN alloys are addressed on the basis of state-of-the-art first-principles calculations. For n-type doping we find that nitrogen vacancies are too high in energy to be incorporated during growth, but silicon and oxygen readily form donors. The properties of oxygen, including DX-center formation, support it as the main cause of unintentional n-type conductivity. For p-type doping we find that the solubility of Mg is the main factor limiting the hole concentration in GaN. We discuss the beneficial effects of hydrogen during acceptor doping. Compensation of acceptors by nitrogen vacancies may occur, becoming increasingly severe as x increases in Al_x Ga_(1-x)N alloys.