LOW-VOLTAGE GaAs-BASED HBTs

The primary objective of this work is to determne the feasibility ofusing nitrogen doping to lower the trun-on voltage and improve the overall performance of GaAs-bsed heterojunction bipolar transistors (HBTs) for high frequency microwave applications. Recent reports on the properties of GaAs in which small amounts of N have been added indicate that GaAsN alloys possess a number of striking properties, including a huge band-gap bowing parameter. We believe these properties make GaAsN an exciting new material system for high performance GaAs-based HBTs. The potential benefits of an HBT structure incorporting GaAsN in the base include lower turn-on voltage, stable current gain, and improved high frequency performance. In additon there are several reasons to believe that N-doping may even improve the long term reliability of GaAs-based HBTs, and that it may reduce the necessity of a passivating ledge for preserving small area device performance. Kopin intends to work closely with both a university and an industrial partner to explore the potential benefits of GaAsN HBTs. This integrated Phase I effort will range from basic material stdies to device fabrication and reliability testing and will aly the ground work for the commercialization of future generations of high frequency microwave circuits.