Improved performances of a two-step passivated heterojunction bipolar transistor

An interesting InGaP/GaAs heterojunction bipolar transistor (HBT) with a two-step passivated (ledge structure and sulfur treatment) process on the base surface has been fabricated and studied. Based on the two-step passivation, improved transistor characteristics including the specific contact resistances ρC, sheet resistances Rsh, base surface recombination current density JSR, base current ideality factor nB, and microwave performances are obtained. Furthermore, the device with two-step passivation reveals the better thermal stability on ρC, Rsh, and nB than the devices with and without ledge structure. Therefore, the two-step passivation method can be employed for high-temperature and low-power electronics applications.