MEASUREMENT OF PHONON-EXCITON DEPHASING RATE IN GAN ON SAPPHIRE BY DEGENERATE 4-WAVE-MIXING

The density and temperature dependence of the exciton dephasing time o f two hexagonal GaN films on sapphire is measured using degenerate fou r-wave mixing (DFWM). The residual 4 ps dephasing time at low temperat ure and density is caused by exciton-impurity scattering. We present a theory of DFWM for various amount of inhomogeneous broadening. Good a greement of the temperature dependence of the dephasing time is found between theory and experiment. (C) 1998 American Institute of Physics.