Abstract:
Wurtzite GaN epilayers are studied by cathodoluminescence (CL) spectroscopy. Results show that
the intensities of donor-acceptor pair (DAP) and yellow luminescence (YL) peaks sublinearly
depend on excitation density, presumably, due to saturation effects. The intensity of near-gap
emission, however, exhibits a superlinear dependence on electron-beam excitation. In contrast to
photoluminescence measurements, CL studies of GaN are usually performed in a regime with a
strongly nonlinear dependence of luminescence intensities on excitation due to a large difference in
carrier generation rates for these two techniques. As a result, the ratios of near-gap to YL and DAP
emission intensities strongly depend on electron-beam current. Moreover, electron-beam spot size
(i.e., beam focusing) dramatically affects CL intensity. An understanding of such saturation effects
is necessary for a correct interpretation of CL spectra from GaN.
