High-performance InP/InGaAs pnp

A high-performance InP/InGaAs $\delta $-doped pnp heterojunction bipolar transistor (HBT) has been first fabricated and demonstrated. The addition of a $\delta $-doped sheet between two undoped spacer layers effectively eliminates the potential spike at emitter-base junction, lowers the emitter-collector offset voltage, and increases the barrier for electrons, simultaneously. Experimentally, a maximum current gain of 50 and a low offset voltage of 70 mV are obtained, respectively. To our knowledge, the offset voltage of the studied device is the lowest value for the reported InP/InGaAs pnp HBTs