Photoelectron spectroscopic investigation of nitrogen chemical states in ZnO: (N,Ga) thin films

Fabrication of high quality p-type ZnO is the main challenge in recent ZnO research that prevents the practical application of ZnO-based devices in optoelectronics. The mechanism behind is thought to be due to self-compensation of native defects and/or dopant-induced donors. In this report, we investigated the chemical bonding states of nitrogen doped ZnO films under monodoping, codoping, and cluster doping with Ga. It was found that the N/Ga flux ratio in the doping process has a critical influence on the chemical bonding of nitrogen in ZnO. By tuning the N/Ga doping ratio, it is expected to create appropriate chemical environments to enhance the formation of desired dopant species: Ga–N2O2 (codoping), Ga–N3O and Ga–N4 (cluster doping) for p-type ZnO.