Cathodoluminescence of homogeneous cubic GaN/GaAs(001) layers

The cathodoluminescence (CL) of cubic (c-) GaN epitaxial layers is investig ated at temperatures between 50 K and 300 K. The low temperature CL spectra show three well resolved emission lines (3.26 eV, 3.17 eV and 3.08 eV) whi ch are due to excitonic, donor-acceptor and free to acceptor transitions. S patially resolved measurements of the intensity of the excitonic emission d emonstrate the homogeneity of the layers which are free of microcrystalline inclusions. The room temperature CL of the layers has a full width at half maximum of 56 meV and is due to excitonic recombination as is concluded fr om the zero-shift of the line position when the excitation intensity is var ied over some orders of magnitude. The intensity of a broad emission band a t 2.4 eV shows a strong nonlinear variation of the intensity at high excita tion levels. Using a rate equation model for the near band edge and the dee p 2.4 eV emission we are able to describe the intensity variation of these radiative transitions as a function of the excitation intensity. Depth reso lved CL measurements reveal a homogeneous depth distribution of deep recomb ination centres responsible for the deep 2.4 eV luminescence band.