N p n N double-heterojunction bipolar transistor on InGaAsP/InP

Abstract

Double-heterojunction bipolar transistors have been fabricated on InGaAs(P)/InP with current gains of up to 200. Transistors with a p+-InGaAs/N-InP base/collector junction exhibited drastic gain reduction at low collector bias voltages which is ascribed to the electron repelling effect of the conduction-band spike formed at the collector heterojunction. To overcome this complication a thin n-InGaAs transition layer was inserted between the ternary base and the InP wide-gap collector. The resulting nN double-layer collector structure leads to excellent current/voltage characteristics.

A vertical monolithic combination of an InGaAsP/InP laser and a heterojunction bipolar transistor

“…A wide gap collector has the advantage of suppressing hole injection from base into the collector under saturation conditions, while allowing the interchangeability of the collector and emitter. To overcome the possible electron repelling effect [8] arising from the abrupt InGaAsP /InP base-collector junction, a thin InGaAsP low bandgap layer was inserted between the InGaAsP base and InP collector layer. Since the structure was grown on an nf-InP substrate to be compatible with conventional laser technology, the HBT was intended to operate in an emitter-down configuration.…”