Application of O+implantation in inverted InGaAs/InAlAs heterojunction bipolar transistors

Deep O+ implantation has been used to create a high-resistivity layer buried beneath the Be+ -implanted extrinsic base-emitter junction region of In0.52Al0.48As/In0.53Ga0.47As inverted (emitter-down) heterojunction bipolar transistors (HBT´s). The O+ -implanted layer remains highly resistive even after a rapid thermal annealing step at 700°C to activate the Be+ implants. With the O+ implantation, the forward current of the extrinsic base-emitter diode is significantly reduced. HBT´s with Be+ - and O+ -implanted extrinsic base regions exhibit current gains of ≃ 100 at a collector current density in excess of 10³A/cm². Another benefit from the deep O+ -implanted layer is a dramatic reduction in the junction capacitance of the extrinsic base-emitter diode.