Intentional anisotropic strain relaxation in (112^¯2) oriented Al_1−xIn_xN one-dimensionally lattice matched to GaN

We report on (112^¯2) oriented Al_1−xIn_xN grown by low pressure metal organic vapor phase epitaxy on (112^¯2) GaN templates on patterned r-plane sapphire. The indium incorporation efficiency as well as the growth rate of (112^¯2) oriented layers are similar to c-plane oriented Al_1−xIn_xN layers. Deposition of thick Al_1−xIn_xN layers does not lead to additional roughening like in case of c-plane oriented Al_1−xIn_xN. Independent of the thickness, the degree of relaxation of layers lattice matched in m-direction is in the range of 33%–45% in [112^¯3^¯]-direction. Associated with the relaxation in [112^¯3^¯]-direction, there is a tilt of the Al_1−xIn_xN layers around the [11^¯00] axis due to slip of threading dislocations on the basal (0001)-plane. Relaxation in m-direction is not observable for layers lattice matched in [112^¯3^¯] direction. The possibility to adjust the lattice parameter of AlInN in [112^¯3^¯] direction without changing the lattice parameter in m-direction by anisotropic strain relaxation opens up opportunities for subsequent growth of optically active structures. One possibility is to form relaxed buffer layers for GaInN quantum well structures.