Photoluminescence from strained InAs monolayers in GaAs under pressure

We have investigated the dependence on hydrostatic pressure of the photoluminescence of InAs monolayers embedded in bulklike GaAs at 10 K and for pressures up to 8 GPa. Below the pressure-induced Γ-X conduction-band crossover in GaAs (4.2 GPa) the optical emission is dominated by direct optical transitions between Γ-like excitonic states bound to the InAs monolayer. With increasing pressure this luminescence band shows a blueshift similar to the lowest direct band gap of bulk GaAs. At pressures above the band crossover two emission bands are observed. These bands, characterized by having negative pressure coefficients, are attributed to the type-I transition between conduction-band ${\mathit{X}}_{\mathit{x}\mathit{y}}$ and heavy-hole states of the InAs monolayer and the type-II transition from X states in GaAs to InAs heavy-hole states. The results are interpreted in terms of tight-binding band-structure calculations for the strained InAs-monolayer–bulk-GaAs system.