The cathodoluminescence spectrum of n-GaN crystal has been
studied with emphasis placed on its self-absorption behavior. An improved
analysis of cathodoluminescence spectral shift with electron penetration
depth is shown, according to the following approach: (i) a main band and a
sub-band, both of Gaussian nature, are used for spectral convolution; (ii)
the observed absorption edge is still described in terms of the Urbach rule,
but the Urbach tail is experimentally retrieved by directly using the
absorption spectrum (at low energies) obtained from standard
cathodoluminescence spectra; (iii) an experimental approach is used to
retrieve the actual morphology of the cathodoluminescence probe.