Device design and fabrication of InGaP/GaAsSb/GaAs DHBTs

by Cheung, Chi-chuen

(Uncorrected OCR) Abstract of thesis entitled Device Design and Fabrication of InGaP/GaAsSb/GaAs DHBTs submitted by Cheung Chi Chuen, Cecil for the degree of Master of Philosophy at the University of Hong Kong in December 2003 A study of the InGaP/GaAsSb/GaAs double heterojunction bipolar transistor (DHBT) is presented. A novel device structure is designed, fully strained pseudomorphic GaAsSb with different Sb (Antimony) compositions is used as the base layer and an InGaP layer is used as the emitter. Thus both eliminates the misfit dislocations and increases the valence band discontinuity at the InGaP/GaAsSb interface. Various aspects of device performance , including the IV characteristics, current gain, ideality factor, current transport mechanism, high frequency performances and the turn on voltage of the InGaP/GaAsSb/GaAs DHBT are investigated. The results indicate that GaAsSb is a promising base material for reducing the turn-on voltage of GaAs HBTs. The thesis is organized into five chapters. Chapter One, an introductory chapter, defines the aim of the study. Chapter Two reviews the relevant literature and discusses the basic principle of the HBT device physics and the DC (direct current) and RF (radio-frequency) characteristics of the HBT devices. Chapter Three describes the device design and fabrication process in detail, and is illustrated with captioned diagrams. Chapter Four discusses and analyzes the experimental results, and is illustrated with appropriate graphs and tables. Chapter Five discusses the significance of the research in summary form, and suggests some practical ideas for future development.