Comparison of defects in crystalline oxide semiconductor materials by electron spin resonance

Abstract

Defects in crystalline InGaZnO4 (IGZO) induced by plasma were investigated using electron spin resonance (ESR). Thermal stabilities and ɡ factors of two ESR signals (A and B observed at ɡ = 1.939 and 2.003, respectively) in IGZO were different from those of the ESR signals observed in component materials such as Ga2O3 (signal observed at ɡ = 1.969), In2O3 (no signal), and ZnO (signal observed at ɡ = 1.957). Signal A in IGZO increased upon annealing at 300 °C for 1 h, but decreased when annealing was continued for more than 2 h. On the other hand, signal B decreased upon annealing at 300 °C for 1 h. The ESR signal in ZnO decayed in accordance with a second-order decay model with a rate constant of 2.1 × 10−4 s−1; however, this phenomenon was not observed in other materials. This difference might have been due to randomly formed IGZO lattices such as asymmetrical (Ga, Zn)O and In-O layers. Defects in signals A and B in IGZO were formed in trap states (at the deep level) and tail states, respectively.