High speed, high power gallium indium phosphide/gallium arsenide HBTs and their application to microwave monolithic integrated circuits (MMICs).

Abstract

The improvement of high speed and high power performance of self-aligned GaInP/GaAs Heterojunction Bipolar Transistors (HBTs) by means of various layer designs such as tunneling emitter, electron launcher designs and double HBTs is studied. The realization of broadband, high-bit-rate transimpedance amplifiers using optimized devices for near future optical telecommunication systems is also addressed. Optimization of ohmic contact and passive elements was carried out. A fabrication technology was developed for Microwave Monolithic Integrated Circuits (MMICs). This was accomplished by a simple wet etching technology combined with Lateral Etching Undercut (LEU). A tunneling emitter, a composite emitter and a double HBT design with optimized collector spacer were studied for improving the high speed performance. These designs showed f_T and f_max values up to 60GHz and 100 GHz which are comparable with other published GaInP/GaAs HBT results. The collector-emitter offset voltage (V_offset) of GaInP/GaAs HBTs was studied using Ni/Ge/Au and Ti/Pt/Au collector contact metals. Experimental and theoretical investigations were conducted to find the V<italic>offset </italic> dependence on collector metal barrier; A passivation process was developed to prevent degradation of the device. DC and RF performance before and after passivation were then compared to evaluate its impact. Various monolithic transimpedance amplifiers were designed, fabricated, and successfully tested based on information obtained from studies of individual active and passive components in terms of circuit topology, high gain and broad band performance. These circuits show a transimpedance gain of up to 47dBO with bandwidth of over 25 GHz and operation rate of 10Gb/sec. Finally, power characterization of various HBTs were conducted and the impact of collector metal, ballast emitter resistor was studied. High power density performance is reported using GaInP/GaAs HBTs grown by Chemical Beam Epitaxy (CBE) technology. A maximum power of 1.08 W (5.4 W/mm) using 10 finger 2 x 20 mum<super>2</super> GaInP/GaAs HBTs was found under class B operation.