Mechanisms for p-type behavior of ZnO, Zn$_{1-x}$Mg$_x$O and related oxide semiconductors

TL;DR

This paper investigates how to induce p-type conductivity in ZnO and related oxides by analyzing defect levels through advanced calculations, revealing defect interactions that enable p-type behavior despite deep individual defect levels.

Contribution

It provides a detailed theoretical analysis of defect interactions and their role in enabling p-type conductivity in ZnO and ZnMgO, advancing understanding of doping mechanisms.

Findings

Defect interactions can create shallow acceptor levels.

Individual N_O defects have deep levels unsuitable for p-type conduction.

Grain boundary effects may facilitate p-type behavior.

Abstract

Possibilities of turning intrinsically n-type oxide semiconductors like ZnO and Zn$_{1-x}$Mg$_x$O into p-type materials are investigated. Motivated by recent experiments on Zn$_{1-x}$Mg$_x$O doped with nitrogen we analyze the electronic defect levels of point defects N$_{{\rm O}}$, v$_{{\rm Zn}}$, and N$_{{\rm O}}$-v$_{{\rm Zn}}$ pairs in ZnO and Zn$_{1-x}$Mg$_x$O by means of self-interaction-corrected density functional theory calculations. We show how the interplay of defects can lead to shallow acceptor defect levels, although the levels of individual point defects N$_{{\rm O}}$ are too deep in the band gap for being responsible for p-type conduction. We relate our results to p-type conduction paths at grain boundaries seen in polycrystalline ZnO and develop an understanding of a p-type mechanism which is common to ZnO, Zn$_{1-x}$Mg$_x$O, and related materials.