Pressure dependence of the valence-band discontinuity in GaAs/AlAs and GaAs/${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As quantum-well structures

We have performed high-pressure photoluminescence measurements on a type-II GaAs/AlAs superlattice at liquid-helium temperatures. The observed indirect transitions were found to have a pressure coefficient of -2.4±0.1 meV/kbar, significantly larger in magnitude than the coefficient of -1.3 meV/kbar reported for the indirect gap of GaAs. This is interpreted as evidence for a pressure dependence of the valence-band discontinuity (Δ$E_V$) of approximately +1 meV/kbar. Our result is in excellent agreement with theoretical calculations of Van de Walle and Martin. Taken together with previously reported data, it suggests that the magnitude of dΔ$E_V$/dP is a linear function of the alloy composition of the barrier material. We show that the fractional conduction- and valence-band offsets of GaAs/${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As are pressure dependent.