Computer Modeling the Excitonic Reflection and Photoluminescence Spectra of GaN Epitaxial Layers

Photoluminescence (PL) and reflection excitonic spectra o f GaN single layer grown on sapphire substrate by MOVPE were modeled with aim to estimate a basie parameters o f free A- and B- excitons. The calculations were performed in the frame o f two-oscillator model for dielectric function e(E). Three layered model o f crystal was used for fitting o f reflection spectrum which was measured at T=80K. In this way the dead layer thickness d=6 nm, resonance energies Eа=3.4916 eV and Eв = 3.5008 eV as well as the broadening parameters Га = 5.27 meV and Гв = 7.14 meV of the free excitons were obtained. These parameters were used then for fitting of PL spectra in assumption o f the thermal equilibrium for excitons taking into account the self-absorption of resonance emission. The values of diffusion coefficients Dа =0.3 cm²/s, Dв = 0.1 cm²/s and exciton lifetimes Ƭa = 37 ps, Ƭв = 17 ps were estimated