Chapter One

V. A. Coleman and C. Jagadish

Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, The Australian National University, Canberra, ACT 0200, Australia

1.1 Introduction

Recently, zinc oxide (ZnO) has attracted much attention within the scientific community as a 'future material'. This is however, somewhat of a misnomer, as ZnO has been widely studied since 1935, with much of our current industry and day-to-day lives critically reliant upon this compound. The renewed interest in this material has arisen out of the development of growth technologies for the fabrication of high quality single crystals and epitaxial layers, allowing for the realization of ZnO-based electronic and optoelectronic devices.

With a wide bandgap of 3.4 eV and a large exciton binding energy of 60 meV at room temperature, ZnO, like GaN, will be important for blue and ultra-violet optical devices. ZnO has several advantages over GaN in this application range however, the most important being its larger exciton binding energy and the ability to grow single crystal substrates. Other favorable aspects of ZnO include its broad chemistry leading to many opportunities for wet chemical etching, low power threshold for optical pumping, radiation hardness and biocompatibility. Together, these properties of ZnO make it an ideal candidate for a variety of devices ranging from sensors through to ultra-violet laser diodes and nanotechnology-based devices such as displays.

As fervent research into ZnO continues, difficulties such as the fabrication of p-