Cross-sectional cathodoluminescence of GaN epitaxial films

Abstract

Cathodoluminescence (CL) in the scanning electron microscope has been used to investigate the variation along the growth axis direction of luminescence emission from epitaxial GaN films. CL spectra recorded at different positions of the sample cross-section as well as monochromatic CL images show strong spatial variations of the different luminescence emissions along the growth axis. At the buffer layer-substrate interface and at the top part of the sample, which corresponds to a Si doped epilayer, enhanced CL emission is observed as compared with the relatively low emission in the central region of the cross-section. The nature of the defects responsible for the observed CL distribution is discussed.