Pseudomorphic ${\mathrm{In}}_{0.17}$${\mathrm{Ga}}_{0.83}$As/${\mathrm{Al}}_{0.32}$${\mathrm{Ga}}_{0.68}$As multiple quantum wells under hydrostatic pressure: Implications for band alignments

Photoluminescence from optically pumped strained-layer quantum wells of ${\mathrm{In}}_{0.17}$${\mathrm{Ga}}_{0.83}$As/ ${\mathrm{Al}}_{0.32}$${\mathrm{Ga}}_{0.68}$As has been observed under hydrostatic pressures up to 100 kbars, using a diamond-anvil cell. High-resolution x-ray diffraction has been used to determine structural parameters. Analytic expressions have been derived for the hydrostatic-pressure dependence of the Γ-band-gap photoluminescence intensity for the case of a heterojunction. This allows us to differentiate between two possibilities: whether an observed pressure-induced Γ-X crossing in a quantum-well structure is indicative of a Γ and X crossing in the well material only, or whether the Γ band edge in the well material crosses the X band edge of the barrier material. Only in the latter case can information on band alignments be obtained. The present heterostructure is found to satisfy the latter criterion, thus allowing the determination of Δ${\mathit{E}}_{\mathit{v}}$≊(0.157±0.025) eV, at ambient pressure.