Large valence-band offset in strained-layer InxGa1-xAs-GaAs quantum wells

We report a determination of band offsets in strained-layer InxGa1-xAs-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 <>Ev,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 <>Ev,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 InxGa1-xAs-GaAs system lattice-matched to GaAs in which the ground state for light holes is localized in the InxGa1-xAs layers. This conclusion is supported by photoluminescence excitation experiments.