The optical properties of thin Al0.3Ga0.7As-GaAs quantum wells on misorientated substrates with (110) terraces. A study of interface roughness using photoluminescence

This study investigates the dependence of the luminescence linewidth from thin quantum wells grown by molecular beam epitaxy on misorientated substrates with (110) terraces of different widths. The narrow luminescence linewidths observed from quantum wells grown on exactly orientated (001) surfaces, 6.7 meV for a five-monolayer well, make them particularly suited to sensing changes in interface roughness associated with either substrate misorientation or growth interruption. An increased luminescence linewidth was found to occur during growth interruption, for example 2.2 meV to 7.2 meV for a 20-monolayer well. This was due to the scale of the roughness at the interface becoming similar in size to that of the sensing exciton wavefunction. The authors suggest this may be related to an increase of the island size at the inverted interface along the (110) direction.