Chapter 2 - Doping and Defects in ZnO

Abstract

This chapter discusses the defects in zinc oxide (ZnO). ZnO is a wide bandgap semiconductor material with numerous present applications, such as varistors and surface acoustic wave devices, and future applications, including UV light-emitting diodes and transparent field-effect transistors. However, all of these applications are either dependent upon, or are affected by, impurities and defects. It considers donor-type impurities H, Al, Ga, and In; and acceptor-type impurities N, P, As, and Sb. Among defects, it concentrates on Zn interstitials, Zn vacancies, O vacancies, and complexes of each. The main experimental techniques discussed in the chapter include temperature-dependent Hall-effect and low-temperature photoluminescence measurements, because they can alone provide donor and acceptor concentrations, and donor energies. Surface conduction is important in the Hall-effect analysis of annealed samples, and it is included by means of a two-layer analysis. The important topic of p-type ZnO is considered in some detail, especially in connection with the most useful acceptor dopants.