Reduction of bound-state and nonradiative defect densities in nonpolar (1120) AlGaN/GaN quantum wells by the use of lateral epitaxial overgrowth technique

Reduction in bound-state and nonradiative defect densities was shown in nonpolar (11-20) Al_xGa_1-xN/GaN multiple quantum wells (MQWs) grown on GaN templates prepared by lateral epitaxial overgrowth (LEO-GaN), in terms of the appearance of correct in-plane light polarization and improved internal quantum efficiency. The (11-20) LEO-GaN grown by halide vapor phase epitaxy exhibited a fairly long photoluminescence (PL) lifetime (τ_PL=530 ps) at 300 K. Structural advantages of using nonpolar orientations were confirmed by a moderate shift of the PL peak energy and negligible change in low-temperature τ_PL with decreasing GaN well width, both of which are the results of eliminating quantum-confined Stark effects due to the spontaneous and piezoelectric polarization which exists in polar (0001) MQWs.