Effect of Source Electrostatic Interaction on the Off-State Leakage Current of p-GaN Gate HEMTs

To assess the reliability of GaN power transistors, off-state leakage characteristic is measured for Schottky p-GaN gate HEMTs under negative gate biases. It is found that the drain leakage current increases abnormally with the decrease of gate-to-source voltage, which is contrary to the situation in normally-on GaN MISHEMTs. It is proposed that the phenomenon is caused by the combined effect of source electrostatic interaction and source-connected field plate, which enhance the electric field near the gate edge on the drain side at negative gate bias. And such effect is more severe in the GaN HEMTs with a p-GaN gate stack due to geometry effect, which enhance the source electrostatic interaction.