Oxide Breakdown in High-Voltage GaN FETs

As the demand for more energy efficient electronics increases, GaN has emerged as an attractive candidate material for high-voltage power management applications. The most promising device structure at the moment is that of a metal-insulator-semiconductor high-electron mobility transistor (MIS-HEMT) in which a gate oxide is placed between the gate metal and the AlGaN/GaN heterostructure of a HEMT. A concern with this new device technology is gate oxide reliability under prolonged high-field and high-temperature conditions. This project studies an important aspect of oxide reliability, time-dependent dielectric breakdown (TDDB) in GaN MIS-HEMTs. We have developed an experimental methodology to characterize TDDB through time-dependent current-voltage and capacitance-voltage measurements. Our techniques isolate and observe different roles of threshold voltage shift, oxide trap formation and trapping, interface state generation, stress-induced leakage current (SILC), and eventual breakdown.