Photoluminescence studies of a GaAs-Ga1−xAlxAs superlattice at 8–300 K under hydrostatic pressure (0–70 kbar)

Abstract

The pressure dependence (0–70 kbar) of the photoluminescence spectra from a GaAs-${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Al}}_{\mathrm{x}}$As multiple-quantum-well (MQW) structure is reported at 8–300 K. The pressure coefficients of the $E_{\mathrm{nh}}^{\Gamma }$ and $E_{\mathrm{nl}}^{\Gamma }$ (n=1, 2) transitions between the Γ conduction subbands and the heavy- (h) and light- (l) hole bands are determined. The energy of $E_{1h}^{\Gamma }$ has a sublinear pressure dependence for the MQW at 80 K but not at 300 K. The reverse is true for the band gap of bulk GaAs. In the MQW the Γ and X bands cross around 35 kbar and a new transition $E_{1h}^X$, observed for the first time, has a pressure coefficient of -1.3±0.1 meV/kbar at 80 K. The X–Γ band separation at atmospheric pressure in the bulk is deduced to be 45–50 meV lower than the previously accepted value of 0.464 eV. The carrier lifetimes in the Γ and X bands and the Γ-to-X scattering times are deduced.