Strain-induced splitting of the valence band in epitaxially lifted-off GaAs films

摘要

We report a detailed study on the valence band splitting in epitaxial lift-off (ELO) GaAs film bonded to silicon. The GaAs film used in this study was grown by molecular beam epitaxy on epiready GaAs (100) substrate. Variable temperature photoluminescence and reflectivity spectra were obtained for the as-grown film, the freestanding ELO film, and the ELO GaAs film bonded to silicon. The PL spectra for the GaAs film on Si showed the removal of the valence band degeneracy with the light hole and heavy hole transitions separated by 4.2 meV at 10 K and decreased monotonously to 1.6 meV at 230 K. No similar splitting was observed for the as-grown and freestanding films. The strain and stress were calculated at ε = (1.2±0.04) X 10~(-3) and X =0.8±0.05 kbar, respectively, at 10 K and ε = (2.3±0.04) X 10~(-4) and X=0.3±0.05 kbar at 230 K. The temperature dependence of the heavy hole-light hole separation energy indicated a strain-induced effect caused by the difference in the coefficient of thermal expansion between GaAs and Si. This shows the efficiency of using ELO techniques on dissimilar materials for strain related spectroscopy.