Self-Heating and Hotspots in GaN HEMTs with Conventional and T-Shape Gates

Self-heating effects and hotspots due to an electric field and a field-induced trap generation are studied in two conventional 1 µm gate length GaN HEMTs with widths of 50 µm and 100 µm, and two Tshaped 250 nm gate length GaN HEMTs with the same gate widths. The study of self-heating and hotspots in the access region between the gate and the drain uses a combination of experiments and TCAD simulations. The simulations are calibrated against experimental I<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</inf>-V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</inf> characteristics at high and low drain voltages assuming a self-heating and a generation of deep carbon traps between the gate and the drain induced by a high electric field. We demonstrate that carbon traps act as deep or shallow traps depending on the GaN HEMT gate architecture and show that the T-gate HEMT architecture exhibits only shallow traps thanks to a more uniform electric field distribution in the drain region.