Large valence-band offset in strained-layer InxGa

We report a determination of band offsets in strained-layer ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$-GaAs quantum wells lattice-matched to GaAs. Using a light-scattering method, we find a large offset for the averaged valence bands, which extrapolates to $\ensuremath{\Delta}{E}_{v,\mathrm{av}}=0.49$ eV in the InAs-GaAs system. This vlaue contradicts previous experimental determinations but agrees with predictions of theories that consider charge-transfer effects at the interface. It follows from some of these theories that $\ensuremath{\Delta}{E}_{v,\mathrm{av}}$ has a surprisingly strong uniaxial strain dependence, a fact that is consistent with our experimental result. Our light-scattering experiment leads to a new band structure for the ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$-GaAs system lattice-matched to GaAs in which the ground state for light holes is localized in the ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ layers. This conclusion is supported by photoluminescence excitation experiments.