Reliability issues for III-V heterojunction bipolar transistors

Abstract

This paper presents an overview of known and potential issues limiting heterojunction bipolar transistor stability and reliability based on material properties, heterojunction interfaces, device fabrication, and electrical and thermal stresses. While there has been remarkable progress in recent years in demonstrating the superior capabilities of GaAs- and InP-based heterojunction bipolar transistors, there remain important, unanswered questions with regard to device stability and reliability due to the immature nature of the technology in these materials systems. Based on published reports, the principal modes of device degradation observed to date in these transistors, such as reduction in the current gain due to Be outdiffusion from the base, will be summarized and the current understanding of their origins discussed. In addition, potential sources of device instabilities will be discussed, such as degradation phenomena observed in other related devices, such as semiconductor lasers and FETs, and reports of instabilities in material properties. The aim of this paper is to provide an improved understanding of the current limits imposed by degradation phenomena to device design, fabrication and operation, and thereby enable the development of more reliable, high performance devices and circuits.