AlGaN/GaN Heterojunction Bipolar Transistors With High Current Gain and Low Specific on-Resistance

N-p-n AlGaN/GaN heterojunction bipolar transistors (HBTs) on sapphire substrates with high current gainβof 129, low specific ON-resistance (RON,sp)of 0.28m Ω ·cm2 and high current densityJCof ~15 kA/cm2 (if normalized to emitter area,RON,sp ~ 0.15 m Ω · m^2andJC ~ 28.4kA/cm2) have been demonstrated. The analysis of component ofRON,spyields the collector resistance is ~5.2% of the totalRON,sp, showing the low ON-resistance advantage of GaN HBTs. The open-base avalanche breakdown voltage (BVCEO) is ~160 V. High-temperature performance of GaN HBT is also evaluated. TheRON,spis reduced as temperature increasing in the range of 25 °C–100 °C due to enhanced hole concentration in the base layer. The cutoff frequency (fT)of greater than 4 GHz is determined atVCE =9 V. These results dominate that GaN HBTs have been anticipated to become a new technology for next-generation power switches and RF power amplifier circuit.