Thermal Effects between Carbon-Doped GaN and AlGaN Back-Barrier in AlGaN/GaN HEMTs on Si (111) Substrates

Carbon-doped GaN and Al 0.05 Ga 0.95 N/Al 0.08 Ga 0.92 N back-barriers are employed as a semi-insulating buffer in AlGaN/GaN high- electron mobility transistor (HEMT) structures on Si (111). The AlGaN buffer exhibits improved breakdown behavior in high temperature operation owing to an additional potential barrier at the bottom of the GaN channel. The vertical and lateral leakage currents are reduced by 10X and 2X, respectively, resulting in 140 V higher reverse vertical breakdown, and 100 V higher lateral isolation breakdown voltage at 150°C. The AlGaN buffer shows slightly inferior room-temperature 2DEG transport properties as well as a roll-off in output characteristic suggesting a higher thermal impedance relative to the carbon-doped buffer. Both buffers are suitable for high-voltage operation, with the AlGaN showing advantageous leakage and breakdown properties at elevated temperature.