ABSTRACT
Zinc Oxide (ZnO) has been regarded as a promising candidate for next generation ultraviolet light-emitting devices, due to its wide band gap, large exciton binding energy, and small exciton Bohr radius. Since both electron and hole injection are mandatory for electrically driven light-emitting devices such as light-emitting diode (LED), n- and p-type doping with electron and hole concentrations well in excess of 1017 cm-3 are necessary. The success in p-type doping of GaN, a material very similar to ZnO in crystal structure and properties, and subsequent commercial utilization of GaN-LEDs and LDs, has inspired great and continuous efforts to overcome the p-type doping of ZnO. While most efforts on p-type doping of ZnO were focused on nitrogen doping, fewer studies had considered other group-V elements. p-type ZnO films have been obtained by using phosphorus dopant. The p-type ZnO is achieved by the effective doping of the impurity band if excess N atoms are available, rather than the traditional co-doping concept.
