Abstract
An oxide confined collector-up heterojunction bipolar transistor (HBT) is proposed to reduce the leakage current and the parasitic capacitance in the extrinsic region. Two-dimensional numerical simulations were used to demonstrate the electrical characteristics of the new HBT structure. The current gain was evidently increased from 0.63 to 42 after the thin Al 0.98 Ga 0.02 As layer was appropriately oxidized, and the forward transport characteristics of the HBT were not obviously degraded by the added thin Al 0.98 Ga 0.02 As layer. The current gain of the HBT was only decreased about 3% to 4% due to the defects existing at the interfaces between the Al-oxide layer and its adjacent layers. Therefore, the proposed oxide confined collector-up HBT is expected to achieve excellent performance in applications of high frequency amplifiers.