Gallium nitride (GaN) epilayers is deposited by metal-organic chemical vapor deposition (MOCVD) on prismatic a-plane (1 1 2 0) of sapphire crystal. The effect of lattice mismatch and the dislocation activity on the physical properties of GaN epilayers after deformation by means of nanoindentation technique was studied. The failure mechanism of GaN is investigated by the cathodoluminescence (CL) analysis. The surface morphology is analyzed using scanning electron microscopy (SEM). Hardness and elastic modulus of the GaN are measured by using depth-sensed nanoindentation testing coupled with force control mode. In order to understand the nanoindentation mechanism and improve subsequently CL emission quality for GaN epilayers, the relation of lattice mismatch and deformation is focused.
