Correlation between kink and cathodoluminescence spectra in AlGaN/GaN high electron mobility transistors

The "kink" effect in AlGaN/GaN high electron mobility transistor current-voltage characteristics is shown to be associated with the epitaxial growth and is unaffected by fabrication process or growth substrate in device wafers from two epitaxy sources and three foundries. We demonstrate that there is a direct correlation between the presence of the "kink" and the presence of a broad yellow cathodoluminescence band. On the basis of generally accepted models for yellow luminescence, we propose that the kink is due to the presence of deep levels in the GaN buffer layer which decrease the drain current when negatively charged.