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 of the density of point defects, while the dislocation configuration is almost unaffected. The density of microdefects is sufficiently reduced after the postimplantation annealing. The structural quality of the AlxGa1-xN layers strongly depends on the Al concentration and is worsen 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.