13.3 Correlation between Luminescence and Current Collapse in AlGaN/GaN HEMTs

Abstract This paper describes experimental results on the correlation between current collapse and electroluminescence observed under high drain bias conditions in AlGaN/GaN HEMTs with high breakdown voltages over 1000 V. The electroluminescence characteristics were categorized into 2 groups: one from the drain edge with a strong white-appearance emission and the other from the whole gate-to-drain area with a weak red-appearance emission. When the luminescence results were compared with the measured current collapse, it was found that the weak red-appearance emission was only observed from the device with reduced current collapse, while the strong white-appearance emission appeared for the device showing strong current collapse. Since clear band edge emission was not detected in the emission spectra, luminescence was likely due to intraband electron transition in the conduction band. A series of analyses of luminescence characteristics from different AlGaN/GaN HEMTs strongly suggest that the current collapse is indeed dominated by the surface trapping effects that arise in relation to the potential profile between gate and drain.