Investigating the Effect of AlGaN Back Barrier in Buffer Free AlGaN/GaN HEMTs with Stacked HfO2/SiN Passivation for High Frequency Applications

GaN HEMTs are essential devices in high-voltage, fast switching operation in 5G and millimeter-wave applications. This research presents an AlGaN/GaN HEMT without buffer (BF-HEMT) featuring an AlGaN back barrier and stacked HfO2/SiN passivation. The device’s characteristics were evaluated using the Sentaurus TCAD tool. Incorporating a 100 nm AlGaN back barrier with 7% Al mole fraction provides strong two dimensional electron gas (2DEG) confinement suppresses leakage and enhanced RF performance, while causing only minor reductions in drain current and transconductance. The proposed device demonstrates a 3.7-fold increase in current-gain cut-off frequency and a 3.8-fold increase in maximum oscillation frequency over conventional HEMTs. Even with a slight reduction in breakdown voltage, the device demonstrated a notable enhancement in Johnson’s figure of merit (JFOM), reaching 14.96 THz·V. The demonstrated balance between high-frequency response and power capability positions the device as a strong contender for next-generation 5G, mm-wave, and power amplifier technologies.