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 In 0.52 Al 0.48 As/In 0.53 Ga 0.47 As 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 10 3 A/cm 2 . Another benefit from the deep O+ -implanted layer is a dramatic reduction in the junction capacitance of the extrinsic base-emitter diode.