Investigation of leakage current of AlGaN/GaN HEMTs under pinch-off condition by electroluminescence microscopy

Results from on-wafer electroluminescence (EL) microscopy on AlGaN/GaN high-electron-mobility transistors with leakage currents varying over four orders of magnitude are presented. In the off-state region the integrated EL intensity is proportional to the leakage current and independent of gate width for the devices under study. The slope of the integrated EL-leakage current dependence is determined by the electrical field in the source-drain direction. The influence of the GaN cap thickness is small or even negligible for higher drain bias. Stress during accelerated aging results in enhanced degradation for areas of enhanced leakage current and/or electric field values.