Electron dynamics in GaN wafers with an inhomogeneous distribution of defects in the depth direction

Abstract

The dynamics of photoexcited electrons in a GaN wafer with an inhomogeneous dislocation density distribution in the depth direction was measured by the near-field heterodyne transient grating method. We investigated the dependence of the interfaces with different dislocation densities, the dependence on the pump wavelength for a sample with a decaying distribution of dislocation density, which gives information on the depth dependence on the carrier dynamics. In the latter experiment, the observed depth region was continuously changed by tuning the wavelength around the band gap of GaN. The responses of the electron dynamics can be fitted with the sum of two exponential decays for all the experiments and only the slower component decayed faster as the dislocation density increased. It was concluded that the faster component corresponded to the trap process of electrons by deep states due to inherent defects in the GaN wafer and the slower component corresponded to the recombination of the trapped electrons at the defect states by dislocation defects.