Workshop 1.1
SiC and GaN Wide Bandgap Device Technology Overview

Mr. Jim Milligan - Cree

Thu, 29 April 2004, 8:00 AM - 12:00 PM

Abstract

This tutorial will review the current status of SiC MESFET and GaN HEMT wide bandgap device technology. These devices potentially offer significant advantages for next generation military systems. Operating at a drain voltage of 48 volts, the higher load-line impedance of these devices enables wider bandwidth power amplifiers than possible in conventional silicon or GaAs technologies. SiC MESFETs achieve a power density of approximately 4.0 W/mm and power added efficiencies of 50% on a repeatable basis and are commercially available in packaged or die formats. Reliability studies conducted on 10-watt parts demonstrate robust device characteristics. DC Accelerated Life tests on twelve 10-Watt SiC MESFETs operating at TJ = 240?C demonstrate an average reduction in saturated drain current of only 8.9% after being stressed for 2,100 hours. This is well within the 20% JEDEC guideline for defining a failure.

In June 2004, Cree announced that commercial SiC MMIC foundry services are now available. The MMIC process is similar to existing GaAs MMIC processes in that it offers thinned (100 mm) substrates, thin-film resistors, high voltage MIM capacitors, and through-wafer vias. The process has demonstrated good yield on large, high power MMIC amplifiers suitable for high power radar applications.

GaN also appears to be very promising as a next generation device technology. Power densities as high as 25 watts per mm of gate periphery have been reported. With ft?s > 40 GHz, GaN devices have the capability of satisfying system device requirements from UHF through millimeter-wave. Unlike SiC, which has demonstrated excellent reliability characteristics, GaN devices are not as mature. Problems with early device degradation have been observed and a status of this work will be presented during the tutorial.

Bio

Mr. Milligan began his career at General Electric, Utica, NY in 1984 where he worked in the design of solid state phased array antennas, T/R modules, and related GaAs MMIC components for Radar and EW applications. During this period, he held technical positions of increasing responsibility in microwave circuit design and engineering management. Mr. Milligan joined Lockheed Martin (Moorestown, New Jersey) in 1994 where he was responsible for the design and development of advanced phased array antenna systems, microwave T/R modules, and GaAs MMIC technology. In 1999, Mr. Milligan joined Cree, Inc. as a program manager responsible for wide bandgap device technology contracts. At Cree, he has held positions of increasing responsibility including the management of Cree's RF/microwave design group. In 2003, Mr. Milligan was also given responsibility for Cree's commercial wide bandgap microwave business that currently includes a line of packaged SiC MESFET transistors and a SiC MMIC foundry service.