Nonlinear behaviors of valence-band splitting and deformation potential in dilute GaNxAs1-x alloys

Photoreflectance and piezoreflectance investigations have been performed on a series of GaNAs layers grown by low-pressure metal-organic chemical vapor deposition on Si-doped GaAs substrate. In addition to the observation of the fundamental band-gap and spin-orbit splitting, the valence-band splitting in thin GaNxAs1-x epilayers strained coherently by the GaAs substrate is observed in these modulation spectra. Comparing photoreflectance with piezoreflectance spectra, we clearly establish the transitions involving the heavy-hole and light-hole bands. We find that the valence-band splitting increases with increasing nitrogen composition, and it decreases with increasing temperature. We point out that the underlying origin of our observation can be attributed to the effect of lattice mismatch between GaNAs film and GaAs substrate. We also find that the deformation potential of GaNxAs1-x does not follow the linear interpolation of those for GaAs and GaN. It shows a strong composition dependence with a bowing in the small composition. (C) 2002 American Institute of Physics.