Ultraviolet light induced hardening in gallium nitride

Abstract

The plasticity of inorganic semiconductors is affected by light irradiation, which is called the photo-plastic effect (PPE). In this study, we examined the PPE of gallium nitride (GaN) by nanoindentation with controlled light conditions. The nanoindentation experiments revealed that the hardness of GaN {0001} surface is increased up to ∼5% under ultraviolet (UV) light irradiation in comparison with one measured in darkness. Transmission electron microscopy observations showed the activation of basal slip and pyramidal slip for both samples indented with UV irradiation and in darkness. It can be suggested that the hardening of GaN is originated from the deterioration of dislocation mobility due to UV irradiation.