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 gain $\beta $ of 129, low specific ON-resistance ( ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}{)}$ of 0.28 $\text{m}\sf \Omega \cdot $ cm2 and high current density ${J}_{C}$ of ~15 kA/cm2 (if normalized to emitter area, ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}} \sim 0.15 \text{m}\sf \Omega \cdot \text{m}^{{2}}$ and ${J}_{C} \sim 28.4$ kA/cm2) have been demonstrated. The analysis of component of ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ yields the collector resistance is ~5.2% of the total ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ , 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. The ${R}_{ \mathrm{\scriptscriptstyle ON},\text {sp}}$ is reduced as temperature increasing in the range of 25 °C–100 °C due to enhanced hole concentration in the base layer. The cutoff frequency ( ${f}_{T}{)}$ of greater than 4 GHz is determined at ${V}_{\text {CE}} =$ 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.