Fully self-aligned InP/InGaAs heterojunction bipolar transistors grown by chemical beam epitaxy with a Schottky collector

A new HBT design for reduction of parasitic effects has been developed to demonstrate the ability of ballistic and quasi-ballistic electron transport into the base to improve HBT dynamic behavior. To reduce both the transit time and the charging time of the base-collector junction electrons are collected by a Schottky contact. As a result the transistor must be collector-up. A fully self-aligned process has been developed for collector-up HBTs. This small cross-type HBT exhibits an attractive potential for fast dynamic behavior. Static behavior has been characterized on test structures grown by chemical beam epitaxy. It has been shown that current injected by the emitter-base junction flows mainly at junction perimeter. Also, it has been demonstrated that the extrinsic base must be over-doped by ion implantation to have small enough access resistance to the base for good dynamic behavior. Static current gains up to 50 have measured for the shortest junction perimeters.<
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