Pressure dependence of photoluminescence in ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs strained quantum wells

Photoluminescence properties of ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs strained quantum wells with well widths from 13 to 120 Å are investigated as a function of hydrostatic pressure (0–45 kbar) at liquid-nitrogen temperature. Pressure coefficients of the ${\mathit{E}}_{1\mathit{h}}^{\mathrm{\Gamma }}$ transitions between the quantized ground levels of the Γ conduction band and the heavy-hole valence band are presented. A weak recombination with a pressure coefficient of -2.6 meV/kbar is identified, which is attributable to the transition related to the crossover of the Γ band in the well layer and the X band in the barrier layer. Correlating this transition to barrier-to-well indirect recombination, the valence-band-offset fraction is given as ${\mathit{Q}}_{\mathit{v}}$=Δ${\mathit{E}}_{\mathit{v}}$/(Δ${\mathit{E}}_{\mathit{v}}$+Δ${\mathit{E}}_{\mathit{c}}$)=0.32 for a sample with indium fraction of x=0.25. The light-hole band is, therefore, inferred to be type II. Furthermore, the pressure coefficient is found to increase with decreasing well widths, which is opposite to that observed in the GaAs/(Al,Ga)As quantum-well system. A calculation based on the envelope-function model is made to interpret this dependence.