Pnp AlGaN/GaN heterojunction bipolar transistors operating at 300°C

We have fabricated Pnp AlGaN/GaN heterojunction bipolar transistors and investigated their common-emitter current-voltage (I-V) characteristics at the temperatures from room temperature to 300°C. Good saturation properties were observed in their common-emitter I-V characteristics. The current gain of 20 at room temperature increased with elevating the temperature. The maximum current gain was as high as 71 at 300°C with the collector current from 20 to 200 μA. This increase in current gain is ascribed to the enhancement in the hole injection efficiency from the p-AlGaN emitter to the n-GaN base as well as the reduction of the device resistance and the improved Ohmic characteristics of the subcollector. These results indicate that PnP HBTs have the potential for high temperature operation.