InP heterojunction bipolar transistor with a selectively implanted collector pedestal

In a mesa structured HBT, a large portion of C_bcoriginates from the extrinsic base-collector region under the base contact. To reduce extrinsic C_bc, an HBT structure with a selectively implanted collector pedestal and MBE growth, under the HBT intrinsic region is reported. The fabrication steps of the device are implant window and Si ion implant, implant mask removal and HT annealing, HBT structure regrowth and triple-mesa HBT fabrication. The results exhibit low I_cbo and hence high junction quality can be obtained in a collector pedestal process incorporating regrowth.