GaN codoping and annealing on the optoelectronic properties of SnO2 thin films

Transparent GaN doped SnO2 thin films were deposited on glass substrates by e-beam evaporation with GaN:SnO2 targets of various GaN weight ratios. The effects of doping level and annealing temperature on the optoelectronic properties of GaN codoped SnO2 thin films were investigated. A conversion from n-type conduction to p-type was observed for GaN doped thin films upon annealing at 440 °C regardless doping level. However, it converted back to n-type conduction at various higher temperatures depending on GaN doping levels. Hole concentration for p-type GaN:SnO2 thin films could be achieved as high as 1.797 × 1019 cm−3 because of the codoping of Ga and N. Hall measurements showed that upon proper thermal treatments, Ga3+-Sn4+ and N3−-O2− substitution reactions occurred in the thin films, which regulated the polarity of conduction and carrier concentration. The formation of No substitutions in the GaN:SnO2 thin films and decomposition of them at certain higher temperature were mainly responsible for the n-p-n conduction transition.