Hydrostatic pressure coefficients of the photoluminescence ofInxGa1−xAs/GaAs strained-layer quantum wells

The photoluminescence of strained ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As quantum wells, with x up to 0.225, grown pseudomorphically between unstrained GaAs barriers, has been studied under high hydrostatic pressure in a diamond-anvil cell. The measured direct-band-gap pressure coefficients show a marked deviation from theoretical predictions; they decrease strikingly below the GaAs value of 10.7 meV/kbar as the well width or the indium content is increased; the pressure coefficient of the band gap in wide wells depends on well composition x as 10.7-6.0x meV/kbar in the samples studied, compared with a predicted variation of 10.7-1.7x meV/kbar calculated with use of third-order elasticity theory. The experimental data could correspond to a composition dependence of the band-gap hydrostatic deformation potential, scra, of -7.99(1-0.47x) eV for small x. We speculate that the anomalously low measured pressure coefficients may be due to an interplay of effects related to disorder and strain in the alloy quantum wells.