Interface roughness of GaAs-AlAs quantum wells grown by molecular-beam epitaxy: Misorientation effects

Abstract

We have studied the atomic steps and/or terraces at the interfaces of GaAs-AlAs quantum wells (QWs) grown by molecular-beam epitaxy on slightly misoriented GaAs substrates from (001) toward [110] with various off angles α=0°, 0.5°, 1°, 2°, and 5°. It was found that the terrace edges at the surface/interface on the misoriented substrates are either randomly spaced or kinked, leading to the broadening of the photoluminescence (PL) linewidth. We have explained the PL data by considering the diffusion length Ldiff of Ga and Al atoms on the growth front, and the average terrace width Loff due to the misorientation, in relation to the exciton size Dex in QWs. Unlike the case of (001) flat substrates, growth interruption has little effect on the reduction of PL linewidth of the QWs on misoriented substrates.