Comparison of compositionally graded to abrupt emitter-base junctions used in the heterojunction bipolar transistor

Abstract

This article describes an experimental study which compares compositionally graded to abrupt emitter-base junctions which are used in the heterojunction bipolar transistor (HBT). It is found that the larger current gains are obtained in devices with abrupt emitter-base junctions. Measurements of electroluminescence emitted from the base region and temperature-dependent current gain indicate that the larger current gain in the abrupt devices is due to a larger base-transport factor. The data presented provide evidence that the injection of hot electrons from an abrupt emitter-base junction is realizable and can result in improved performance of the HBT.