Patent ID: 7304333
Filing Date: 2007-12-04
Classification: H01L

Abstract:
1. A heterojunction bipolar transistor comprising: a first conductive type collector layer; a first conductive type subcollector layer with a doping concentration higher than the collector layer; a second conductive type base layer; a first conductive type emitter layer, wherein the first conductive type subcollector layer, the second conductive type base layer, and the first conductive type emitter layer are formed, in order, on a semi-insulating semiconductor substrate; and a hole barrier layer of semiconductor material with a band gap wider than that of the second conductive type base layer is disposed between the second conductive type base layer and the first conductive type collector layer, such that the hole barrier layer is in direct contact with the second conductive type base layer, wherein a thickness of said hole barrier layer is 4 nm or greater, and less than 10 nm.