SiGe-Silicon Germanium technology
Silicon-Germanium (SiGe) technology is the driving force behind the explosion in low-cost, lightweight, personal communications devices like digital wireless handsets, as well as other entertainment and information technologies like digital set-top boxes, Direct Broadcast Satellite (DBS), automobile collision avoidance systems, and personal digital assistants. SiGe extends the life of wireless phone batteries, and allows smaller and more durable communication devices. Products combining the capabilities of cellular phones, global positioning, and Internet access in one package, are being designed using SiGe technology. These multifunction, low-cost, mobile client devices capable of communicating over voice and data networks represent a key element of the future of computing.
The heart of SiGe technology is a SiGe heterojunction bipolar transistor (HBT), which offers advantages over both conventional silicon bipolar and silicon CMOS for implementation of communications circuits. My SiGe research at Auburn includes the design, optimization, and testing of state-of-the-art SiGe heterojunction bipolar transistors and integrated circuits. We work closely with IBM, a world leader of SiGe technology since 1982, and the first company to broadly manufacture SiGe technology. The following gives an overview of this fascinating technology.
1. History of SiGe Technology
The concept of combining silicon (Si) and germanium (Ge) into an alloy for use in transistor engineering is an old one, and was probably envisioned by Shockley in his early transistor game. However, because of difficulties in growing lattice-matched SiGe alloy on Si, this concept is reduced to practical reality only in the last 15 years. SiGe HBT technology was originally developed at IBM for the high-end computing market, that effort, however, failed to CMOS, primarily because of its high power consumption.
In the early 1990s, IBM refocused its SiGe program towards the rapidly developing communications market. Interestingly, for RF communications circuits, SiGe HBT consumes much less power than CMOS to achieve the same level of performance. Since then, significant progress has been made. SiGe technology is being developed and applied around the world, and is in the product roadmap of every major telecommunication company. Applications range from wired and wireless communications circuits, to disk storages, to high speed high bandwidth instrumentation. The use of discrete SiGe HBTs and amplifiers in wireless devices is common place. Integrated SiGe chips can be found in GSM and CDMA wireless handsets and base stations, wireless LAN chipsets, and high-speed 10-40 Gb/s synchronous optical network (SONET) transceivers.