Cathodoluminescence studies of point defects in aluminum nitride

Abstract

There is near-ultraviolet and yellow light absorption in AlN crystal. The defect of this absorption hampers the transmittance of ultraviolet light, which, in turn, limits the application of aluminum nitride substrate in deep ultraviolet electronic devices. In this paper, the sources of absorption defects are determined through the first principle simulation method and the cathodoluminescence test of four samples with different growth modes on two substrates. The peak positions of the two AlN grown by metal–organic chemical vapor deposition were observed at 370 and 480 nm; two AlN samples grown by hydride vapor phase epitaxy only observed luminescence near 370 nm. Through the characterization of sample components by x-ray photoelectron spectroscopy, it is speculated that O impurity component and Al vacancy in AlN crystal form donor–acceptor pairs, which are the source of 370 nm luminescence; with the increase in O concentration, a composite defect with Al vacancy is formed, which is the source of 480 nm luminescence. This is very important for further research on eliminating impurity absorption in an AlN epitaxial layer.