Sulfur- and InGaP-passivated heterojunction bipolar transistors

We have been successfully implemented for the InGaP/GaAs heterojunction bipolar transistors (HBTs) with the sulfur-treated GaAs base layer comparing with HBTs fabricated using emitter-edge thinning InGaP layer. As compared with non-passivated HBTs with an exposed extrinsic GaAs base, the improved base leakage current for InGaP-passivated HBTs is due to the inherent low surface recombination velocity associated with an InGaP layer. In views of the sulfur-passivated HBTs exhibited an enhanced current gain is attributed to the modification of the GaAs surface electronic properties. The maximum dc current gain available is 75 at low base current for sulfur-passivated HBTs. The sulfur-passivated devices also exhibit very good linearity in wide range of collector (10^-5 to 10^-1 A). Furthermore, detailed sulfur-treatment conditions and effects on device performance are investigated.