On the mechanism of damage buildup in gallium nitride

Abstract

Damage buildup and defect transformations in ion bombarded in GaN have been studied by the complementary use of Rutherford backscattering spectroscopy/channeling, high-resolution transmission electron microscopy and high-resolution X-ray diffraction (HRXRD) techniques. Ion bombardment was performed at room temperature with Ar ions. Parameters of the damage buildup were evaluated in the frame of the multi-step damage accumulation model. Three step damage accumulation process has been revealed. HRXRD analysis has indicated that ion bombardment to low fluences produces increase of the lattice parameter leading to a strain buildup in the implanted region. Once the critical value of the stress has been attained, plastic deformation due to the dislocation slip takes place leading to the formation of dislocations tangle. At this stage, channeling yield saturates well below the amorphization level. The transition to stage III – amorphization – takes place at high-impurity concentration and is apparently due to the defect–impurity interaction.