The effect of ion implantation on structural damage in compositionally graded AlGaN layers

Abstract

Compositionally graded AlₓGa₁₋ₓN alloys with the Al concentration in the (7 ≤ x ≤ 32) range were implanted with Ar+ ions to study the structural and strain changes (strain engineering). It was shown that ion implantation leads to ~0.3…0.46% hydrostatic strains and a relatively low damage of the crystal structure. The ion-implantation leads mainly to an increase in the density of point defects, while the dislocation configuration is almost unaffected. The density of microdefects is sufficiently reduced after the post implantation annealing. The structural quality of the AlₓGa₁₋ₓN layers strongly depends on the Al concentration and worsens with increasing Al. The implantation-induced structural changes in highly dislocated AlₓGa₁₋ₓN layers are generally less pronounced. Based on the X-ray diffraction, a model is developed to explain the strain field behavior in the AlₓGa₁₋ₓN/GaN heterostructures by migration of point defects and strain field redistribution. The approach to simulate 2θ/ω scans using statistical dynamical theory of X-ray diffraction for implanted compositionally graded structures, AlGaN, has been developed.