1. Introduction

Extensive research is currently carried out on ZnO as a potential material for the fabrication of optoelectronic devices such as photodiodes, laser diodes (LDs) and light-emitting diodes (LEDs) in the ultraviolet region because of its wide bandgap (3.437 eV at 2 K) and a large excitonic binding energy of 60 meV at room temperature. However, because of intrinsic defects such as oxygen vacancies and zinc interstitials, ZnO is intrinsically deposited as an n-type material. Being a II–VI semiconductor compound, group I and group V elements are considered suitable p-type dopants for ZnO. In this monograph, authors concentrate mostly on the different methods undertaken to achieve strong, reliable and stable p-type ZnO films. Ion implantation, being a suitable technique to achieve selective and localised doping, was used to dope ZnO with different group I and group V elements. Lithium and phosphorus ions were implanted using the conventional ion implantation technique, while plasma immersion ion implantation was used to implant phosphorus and nitrogen ions in the ZnO thin films. Such studies would bring interesting revelations in the optoelectronics field for the ultraviolet range and help to produce devices for the commercial market at a much cheaper cost.