PHOTOLUMINESCENCE FROM STRAINED INAS MONOLAYERS IN GAAS UNDER PRESSURE

We have investigated the dependence on hydrostatic pressure of the pho toluminescence of InAs monolayers embedded in bulklike GaAs at 10 K an d for pressures up to 8 GPa. Below the pressure-induced GAMMA-X conduc tion-band crossover in GaAs (4.2 GPa) the optical emission is dominate d by direct optical transitions between GAMMA-like excitonic states bo und to the InAs monolayer. With increasing pressure this luminescence band shows a blueshift similar to the lowest direct band gap of bulk G aAs. At pressures above the band crossover two emission bands are obse rved. These bands, characterized by having negative pressure coefficie nts, are attributed to the type-I transition between conduction-band X (xy), and heavy-hole states of the InAs monolayer and the type-II tran sition from X states in GaAs to InAs heavy-hole states. The results ar e interpreted in terms of tight-binding band-structure calculations fo r the strained InAs-monolayer-bulk-GaAs system.