High-pressure photoluminescence study of GaAs/${\mathrm{GaAs}}_{1\mathrm{-}\mathit{x}}$${\mathrm{P}}_{\mathit{x}}$ strained multiple quantum wells

We report low-temperature photoluminescence studies of GaAs/${\mathrm{GaAs}}_{1\mathrm{-}\mathit{x}}$${\mathrm{P}}_{\mathit{x}}$ strained quantum-well samples grown by gas-source molecular-beam epitaxy as a function of pressure. We have found that the transitions between the lowest Γ-confined electron and hole states shift toward higher energy with increasing pressure, and also that the pressure coefficients of the transitions depend on the alloy concentrations and the quantum-well structures. From the observation of the pressure-induced crossover of the lowest Γ-confined electron state in the wells against the conduction-band (001) X minima in the barriers, we are able to determine the valence-band offset for the GaAs/${\mathrm{GaAs}}_{0.68}$${\mathrm{P}}_{0.32}$ heterostructure. At this crossover point, the emission of Γ-Γ transition quenches and the emission with the characteristics of the X minima becomes dominant. We have also observed an emission associated with a deep center which becomes active with pressure above ∼17 kbar, from the GaAs/${\mathrm{GaAs}}_{0.61}$${\mathrm{P}}_{0.39}$ multiple-quantum-well sample. The pressure dependence of the emission suggests the localized state to be donorlike and resonant above the bottom of the conduction band at ambient pressure.