Effect of strain on the band structure of GaAs and In0.2Ga0.8As

The valence-band structures of 50-Å-thick layers of GaAs(001) in tension and In0.2Ga0.8As(001) in compression have been determined using angle-resolved photoemission spectroscopy. Our studies show that the Δ3+Δ4 bands and the Δ1 band respond differently to the strain perturbation. For strained GaAs(001), the Δ3+Δ4 bands (Px+Py-like) are shifted up in energy by a maximum amount of 0.3 eV, while in contrast, the Δ1 band (Pz-like) is shifted down by about 0.1 eV. For strained In0.2Ga0.8As(001), the band shifts are in the opposite direction, consistent with the opposite strain conditions. For both materials, the strain-induced changes cannot be characterized simply by rigid band shifts, but rather exhibit significant wave vector dependence. This results in a reduction of the effective mass of the Δ3+Δ4 bands for both GaAs and In0.2Ga0.8As.