Temperature independent current blocking in InAlAs/InGaAs double heterojunction bipolar transistors with composite collectors

We have measured current blocking in InAlAs/InGaAs double heterojunction bipolar transistors with composite collectors. The current blocking is almost independent of temperature, in contrast to InP/InGaAs devices, where the blocking strongly increases as temperature is reduced. We attribute the temperature independence in InAlAs/InGaAs devices to electrons that are not thermalized as they cross the base. Our results have implications in the design of collectors for InAlAs/InGaAs DHBTs.