State mixing in InAs/GaAs quantum dots at the pressure-induced Γ-X crossing

We have measured low-temperature (T=10 K) photoluminescence spectra of InAs quantum dots embedded in a GaAs crystalline matrix under hydrostatic pressures up to 7 GPa. Below 4.2 GPa the spectra are dominated by the emission related to the Γ-like electron–heavy-hole exciton in the InAs dots. Above 4.2 GPa the spectra show two luminescence bands that shift to lower energies with increasing pressure. These bands are attributed to the type-I transition between ${\mathit{X}}_{\mathit{x}\mathit{y}}$ and heavy-hole states in the dots and the type-II transition from X states in GaAs to InAs heavy-hole states, respectively. In the Γ-X crossover regime we find evidence for a pronounced anticrossing behavior due to mixing between InAs Γ-like and GaAs X-like states. The corresponding interaction potential is estimated to be 9 meV, which is an order of magnitude larger compared to mixing interactions reported for semiconductor superlattices.