N Doping and Al-N Co-doping in Sol-Gel ZnO Films: Studies of Their Structural, Electrical, Optical, and Photoconductive Properties

We have studied the structural, electrical, optical, and optoelectronic properties of N-doped and Al-N co-doped ZnO films grown by sol-gel technique. Both the undoped and doped films have a hexagonal wurtzite-type structure. The undoped film shows a very low electron concentration. The N-doped film exhibits an anomalous conduction type, while the Al-N co-doped film shows relatively stable p-type conduction. Though the transparency in the visible region is retained in the doped films, its optical qualities are degraded as indicated by photoluminescence results. The N-doped film has better response to ultraviolet light compared with the undoped and co-doped films. These results are important for the growth and development of p-type ZnO films using the very low-cost sol-gel method.