Deep-level spectra from a series of undoped films, having differing GaN buffer growth rates, were studied by means of transient spectroscopy, transmission electron microscopy and high-resolution X-ray diffraction. Two distinct deep levels were observed. One had an activation energy of 0.19 to 0.23eV, and the other had an activation energy of 0.50 to 0.60eV, below the conduction band. A broadening of the (102) Bragg peak with decreasing buffer growth-rate was related to an increasing edge dislocation content. A logarithmic dependence of the deep level transient spectroscopic peak intensity, upon the filling pulse time, indicated that the deep level, E1, was associated with dislocation core sites.

Electron Traps and Growth Rate of Buffer Layers in Unintentionally Doped GaN. H.K.Cho, K.S.Kim, C.H.Hong, H.J.Lee: Journal of Crystal Growth, 2001, 223[1-2], 38-42