A high-breakdown and low-offset voltage InGaP/GaAs heterostructure bipolar transistor for power system applications

Due to the high bandgap (E _g =1.9eV) and etching selectively of In _0.5 Ga _0.5 P material, the InGaP/GaAs material system has been proposed to replace the AlGaAs/GaAs. Undoped or lighted doped InGaP, with a relatively high resistance, was considered well as an "insulator". The wide bandgap characteristics enhance the breakdown voltage and, thus, the power handling capabilities of the device for high power applications. From the device point of view, the high breakdown voltage is an important requirement for high power operations. The wide-gap InGaP was also used to increase the collector breakdown voltage in an NpN double heterojunction bipolar transistors (DHBT's). For InGaP/GaAs DHBT's, the electron blocking effect associated with the presented ΔE _C between B-C heterojunction could cause a degraded current gain. Therefore, it is necessary to suppress the electron blocking effect which mainly resulting from the ΔE _C at BC heterojunction. In this paper, a new InGaP/GaAs heterostructure transistor with a δ-doped wide-gap collector structure has been fabricated successfully and demonstrated. The studied device takes the advantages of the heterostructure-emitter bipolar transistor (HEBT) and DHBT devices. Due to the employed effective E-B homojunction and the δ-doped sheet between base-collector junction, the lower offset and saturation voltages may be achieved.