Submicron scaling of AlGaAs/GaAs self-aligned thin emitter heterojunction bipolar transistors (SATE-HBT) with current gain independent of emitter area

A new, self-aligned process technology for AlGaAs/GaAs heterojunction bipolar transistors (HBT) has been developed, which is based upon ultrathin (100-200 AA) AlGaAs emitter layers. The thin AlGaAs emitter is used as a selective etch stop layer for contacting the p⁺ base layer and acts as an integral surface passivation layer which eliminates recombination currents in the extrinsic base region. This novel technology yields transistors with emitter dimensions as small as 0.3*4.0 mu m² and current gain values independent of emitter area.