Lattice-mismatch-strain effects on excitons In GaAs_(1-x)N_x/GaAs heterostructures

摘要

We have investigated the lattice-mismatch-strain effect on excitons in GaAs_(1-x)N_x (500 nm)/GaAs heterostructures with x - 0.4, 0.8. and 1.5% grown on a GaAs substrate using photoreflectance spectroscopy that is sensitive to excitonic transitions. It is found that the heavy-hole (HH) and light-hole (LH) excitons of the GaAs_(1-x)N_x layer, which are degenerate in a bulk crystal, are split and that the energy of the LH exciton is lower than that of the HH exciton. In this case, a quantum-size effect is negligible because the GaAs_(1-x)N_x layerrnthickness is sufficiently thick. The HH-LH splitting energy increases with an increase of nitrogen concentration (x) in addition to a drastic decrease of the energies of the HH ani LH excitons. We have quantitatively analyzed the nitrogen-concentration dependence of the energies of the HH 38d LH excitons, taking account of the lattice-mismatch-strain effect on the band structure and nitrogen-induced giant boding of the band-gap energy.