Welcome to the home page of Professor John D. Cressler at Georgia Tech! My team specializes in research in next-generation mixed-signal (i.e., RF, microwave, mm-wave, analog, and digital) semiconductor device technologies utilizing atomic-scale bandgap engineering. At present our research focus is heavily on silicon-germanium heterojunction bipolar transistor (SiGe HBT) technology.

Microelectronic device and circuit designers have long sought to combine the superior transport properties and design flexibility offered by bandgap engineering (as routinely practiced in compound semiconductors such as GaAs and InP), with the high yield and low cost of conventional Si fabrication. With the introduction of epitaxial SiGe alloys, that dream has finally become a reality. The SiGe HBT is the first practical bandgap-engineered device to be realized in the Si material system. The first functional SiGe HBT was demonstrated in 1987, and the technology has matured rapidly, at present achieving a unity-gain cutoff frequency well above 300 GHz, circuit delays below 5 picoseconds, and integration levels sufficient to realize a host of record-setting digital, analog, RF, and microwave circuits. Naturally-compatible integration of SiGe HBTs with best-of-breed Si CMOS to form a SiGe HBT BiCMOS technology is an obvious fit for addressing emerging system-on-a-chip and system-on-a-package IC solutions, and is currently being pursued worldwide in the commercial sector. SiGe technology is thus expected to play a major role in the rapidly emerging twenty-first century communications’ electronics infrastructure.

My research team has a very broad focus in this arena, ranging from materials, to devices, to circuits, to systems, and including: fundamental device theory, the understanding of broadband noise and linearity, profile optimization for a given circuit metric, 2-D/3-D device-level simulation and TCAD, compact modeling, cryogenic operation, and radiation effects. We are particularly interested in the fundamental understanding of how device-level engineering (with SiGe) couples to mixed-signal circuit-level performance (i.e., device-circuit interactions).

We enjoy access to state-of-the-art hardware, fabrication support for our circuit designs, and close industrial collaborations. We employ theory, numerical simulation, sophisticated measurements in our state-of-the-art research laboratory, as well as device and circuit design, to help define the future in SiGe.

We are doing exciting things, and I welcome the opportunity of sharing that excitement with you. Please take a moment and explore a little! Feel free to contact me if you have any questions. Thanks, and have a great day!

16 channel SiGe BiCMOS
REU Digital Control ASIC

16 channel SiGe BiCMOS
REU Sensor Interface ASIC

Self-Healing Receiver

Four Element 94 GHz Transmit Receive Phased-Array System