Effects of Zn doping in the substrate on the quantum well intermixing in GaAs/Al_0.24Ga_0.76As single quantum well structures

Zn diffusion usually enhances the intermixing in GaAs/AlGaAs quantum well structures. However, Krames et al reported the reduction of layer intermixing in GaAs/AlGaAs quantum well heterostructures by an initial low-temperature "blocking" Zn diffusion. Zn is commonly used as the dopant of the p-type GaAs substrate. To the best of our knowledge, the effect of Zn diffusion from the Zn-doped GaAs substrate on the intermixing has not been studied. In this work, we report the suppression of GaAs/AlGaAs quantum well intermixing by Zn doping in the GaAs substrate. Three samples with single GaAs/Al_0.24Ga_0.76As quantum wells were used in the work, all grown together by molecular beam epitaxy, but on three different substrates: Zn-doped p-type GaAs, Si-doped n-type GaAs, and semi-insulating GaAs. The samples were annealed together in a rapid thermal processor at temperatures around 900°C. Photoluminescence measurements were then performed to characterize the samples. The sample with Zn-doped GaAs substrate shows more than 50% suppression of quantum well intermixing compared to the other two samples. It is due to Zn diffusion from the substrate into the quantum well, which induces the reduction in the number of group-III vacancies in the quantum well structure.