Short-Circuit Failure Modes and Mechanism Investigation of Ohmic-Gate GaN HEMT

This article studies the short-circuit (SC) failure modes and mechanism of ohmic-gate GaN high electron mobility transistors (HEMTs) through experimental evaluation and numerical investigation. Two distinct SC failure modes of ohmic-gate GaN HEMT have been identified: gate-source SC failure and rapid thermal runaway failure. The SC capability and failure mode of ohmic-gate GaN HEMT are significantly influenced by both the dc bus voltage and gate injection current. Thermal-mechanical simulation and failure analysis techniques are used to identify two SC failure mechanisms: thermal-mechanical stress-induced structural failure and thermal breakdown of the gate GaN/AlGaN heterostructure. The gate injection current is found to be a crucial factor in improving the SC ruggedness of ohmic-gate GaN HEMT under high bus voltage SC conditions.