Influence of excitonic oscillator strengths on the optical properties of GaN and ZnO

摘要

We report on an extensive study of the excitonic properties of GaN and ZnO bulk samples with an accurate determination of excitonic parameters by linear and nonlinear spectroscopics. The in-depth comparative study is carried out between these two competitive wide band gap semiconductors for a better understanding of damping processes. In GaN, it is shown that due to microscopic disorder, such as lattice strain fluctuations, inhomogeneous broadening prevails over homogeneous broadening at low temperature. The opposite situation occurs in ZnO, where the homogeneous broadening dominates due to resonant Rayleigh scattering of exciton polaritons and their interaction with acoustic phonons. This comparative study also allows us to highlight the influence of oscillator strengths on spectrally resolved four-wave mixing and time-integrated four-wave mixing.