High-power characteristics of GaN/InGaN double heterojunction bipolar transistors

High-power characteristics have been investigated for GaN/InGaN double heterojunction bipolar transistors (HBTs) on SiC substrates. A base-collector diode showed a high breakdown voltage exceeding 50 V, which is ascribed to a wide band gap of a GaN collector. The maximum collector current is proportional to the emitter size in the emitter-size ranging from 1.5×10−5 to 1.4×10−4 cm2. The corresponding maximum collector current density is as high as 6.7 kA/cm2, indicating the high current density characteristics of bipolar transistors. A 50 μm×30 μm device operated up to a collector–emitter voltage of 50 V and a collector current of 80 mA in its common-emitter current–voltage characteristics at room temperature. The corresponding power density is as high as 270 kW/cm2, showing that nitride HBTs are promising for high-power electronic devices in terms of both the material and the device structure.