BIAXIAL STRAIN DEPENDENCE OF EXCITON RESONANCE ENERGIES IN WURTZITE GAN

We have systematically studied the strain dependence of the free-excit on resonance energies in wurtzite GaN by photoreflectance measurements using well-characterized samples. The experimental data have been ana lyzed using the appropriate Hamiltonian for the valence bands in wurtz ite GaN and determined the values of the crystal field splitting, the spin-orbit splitting, the shear deformation potential constants, and t he energy gap in the unstrained crystal. Discussions are given on the strain dependence of the energy gaps, of the effective masses, and of the binding energies for the free-exciton ground states as well as on the valence-band parameters. (C) 1997 American Institute of Physics.