High-temperature (300 °C) operation of npn-type GaN/InGaN double heterojunction bipolar transistors

We investigated high-temperature (300 °C) characteristics of npn-type GaN/In_0.07Ga_0.93N double heterojunction bipolar transistors (DHBTs). The current gain obtained at 300 °C is as high as 308, although it decreases with increasing temperature. In Gummel plots, both base and collector current increases with increasing base-emitter voltage. While the maximum collector current at 300 °C is similar to that at room temperature (RT), the maximum base current monotonically increases with increasing temperature. Consequently, the reduction of the current gain with temperature is attributed to the increase in the base current. Since the activation energy of the reduction of the current gain is larger than the expected value assuming the increase in the hole backinjection current from the base into the emitter, an increase in the carrier concentration of the p-In_0.07Ga _0.93N base with temperature is considered to be attributed to the reduction of the current gain.