Anisotropic in-plane strains in nonpolar AlN and AlGaN (112¯) films grown on SiC (112¯) substrates

Abstract

Nonpolar Al1−xGaxN (0≤x≤0.196) (112¯0) films were grown on 4H-SiC (112¯0) substrates by metal organic vapor phase epitaxy. Al1−xGaxN (0≤x≤0.057) films grew almost pseudomorphically on the substrates due to balanced in-plane stresses along [0001] and [11¯00], while Al1−xGaxN (0.057<x) films were strained along [0001] but partially relaxed along [11¯00] due to the absence of the balance. The crystal tilts of the films toward [0001] decreased monotonically with increasing Ga composition due to the correspondence between the (0001) plane distances of the films and the (0002) plane distance of substrates and due to a decrease in the in-plane strain along [0001].