Anisotropic lattice relaxation in non-c-plane InGaN/GaN multiple quantum wells.

We investigate anisotropic lattice relaxation in non-c-plane InGaN/GaN multiple quantum wells (MQWs). Transmission electron microscopy analyses of semipolar [formula] MQWs reveal that lattice relaxation preferentially occurs along the [formula] direction by introducing misfit dislocations (MDs) with a Burgers vector of [formula]. To theoretically describe this anisotropic relaxation phenomenon, we expand the force-balance model, where the competition between the force induced by lattice mismatch and the tension of dislocations determines the motion of dislocations. Furthermore, because MDs are introduced at the interface between the bottom InGaN QW and the underlying GaN, we propose to treat InGaN/GaN MQWs as InGaN single layers with effective In compositions. Applying this structure model to the theoretical calculation of the critical layer thicknesses reproduces well the experimentally observed lattice relaxation. This achievement enables us to design semipolar InGaN/GaN MQW structures without lattice relaxation, thereby realizing higher internal emission quantum efficiencies. [ABSTRACT FROM AUTHOR]