Elastic strain relaxation and piezoeffect in GaN-AlN, GaN-AlGaN and GaN-InGaN superlattices

Abstract

We calculated the elastic strain relaxation in (GaN)n-(AlN)n, (GaN)n(AlxGa1−xN)n and (GaN)n(InxGa1−xN)n superlattices where n is the number of layers in the superlattice cell. This calculation and a similar calculation for a semiconductor–insulator–semiconductor structure allowed us to determine the lower and upper bounds for the elastic strain relaxation in (GaN)m(AlN)n superlattices with arbitrary n/m ratios, i.e., we determine a full range of the critical thicknesses for GaNm(AlN)n superlattices. The obtained theoretical results can also be applied to other superlattices based on III nitrides and their solid solutions. Our theory agrees with the experimental data for GaN-AlN superlattices. Also, we show that the piezoelectric effect may cause a large shift of the absorption edge in defect-free GaNm(AlxGa1−xN)n superlattices.