Download III-Nitride Heterojunction Field Effect Transistors

INSTITUTE OF ELECTRICAL AND ELECTRONIC ENGINEERS
WAVES AND DEVICES
PHOENIX CHAPTER
February 22, 2006 EDS Meeting
www.eas.asu.edu/~wadweb
III-Nitride Heterojunction Field Effect Transistors
Prof. Lester F. Eastman
Cornell University
ECE and CNF
Abstract
The physical basis, technology and performance of AlGaN/GaN FET’s with their undoped polarizationinduced, two-dimensional-electron-gases (2DEG’s) will be presented. The unique properties of the Wurtzite
heterojunction crystals involved include 1x1013/cm2 electron sheet density, 3 megavolt/cm electric field strength, and
the electron transit velocity up to 1x10 7 cm/s. Means of making ohmic contact to the 2DEG’s as well as the the
Schottky barrier gate to control the drain current, and the Si 3N4 passivation of the exposed semiconductor surface to
stabilize its charge will be included. Using simple mushroom-shaped-cross-section gates, power levels to
>11W/mm, and 10W for 1.5mm periphery will be shown.
The limits of Al composition and thickness of the strained, pseudomorphic AlGaN barrier are included, and
layered structures are presented. The Ni/Au gate metal cross-section shape will be explained, as the means of
obtaining 120 Ω/mm gate resistance for 0.25 μm gates. The experimental and analytical aspects of the layout
pattern, and its impact on power-added efficiency will be explained. The short-fall of electron transit velocity, from
its prediction based on Monte Carlo simulations, will be explained in terms of a pile-up of longitudinal optical
phonons in the channel. Velocity overshoot measurements by Dr. Michael Wrabach will be reviewed and explained.
A comparison of similar effects in SiC MESFET’s will also be made. A plan for using doped channels, to limit the
electron density will be presented. Finally, the figure of merit of GaN, SiC and metamorphic GaAs structures will
be compared.
Biography
Lester F. Eastman joined the faculty of Electrical Engineering at Cornell in 1957, and also serves as a member of
the graduate fields of Applied Physics and Materials Science. Since 1965, he has been doing research on compound
semiconductor materials, high speed devices, and circuits, and has been active in organizing workshops and
conferences on these subjects elsewhere since 1965 and at Cornell from 1967. In 1977, he joined other Cornell
faculty members in obtaining funding and founding the National Research and Resource Facility for Submicron
Structures at Cornell (now Cornell Nanofabrication Facility). Also in 1977, he founded the Joint Services
Electronics Program and directed it until 1987. He has supervised 120 Ph.D. theses, over 50 M.S. theses, and over
50 post-doctoral studies. In his research group, effort is underway on III-nitride molecular beam epitaxy, microwave
transistors, and fundamental phenomena. He was a member of the U.S. Government Advisory Group on Electron
Devices from 1978-1988, and has served as a consultant for several industries. From 1987-1993 he served as a
member of the Kuratorium (Visiting Senior Advisory Board) of the Fraunhofer Applied Physics Institute in
Freiburg, Germany. He has been a Fellow of IEEE since 1969, a member of the National Academy of Engineering
since 1986, and has been appointed the John L. Given Foundation Chair Professor of Engineering at Cornell in
January 1985. The IEEE honored him with their 1999 Graduate Teaching Award and the 2000 Third Millennium
Medal. In 2001, he was made Fellow of the American Physical Society. He is the recipient of the 2002 J.J. Ebers
Award of the IEEE Electron Device Society. In 2002, the IEEE “Lester Eastman Conference” on High Performance
Devices, to be held biannually, was established.
Date: February 22, 2006
Location: Bernoulli Conference Rm, Bldg 99, Freescale Semiconductor, 2100 E. Elliot Rd., Tempe, AZ
Drive North on Country Club off Elliot on the western edge of the Freescale site, enter back parking lot
Time: 3:30 - 4:30 pm Presentation
For more information, please call Chuck Weitzel (Chapter Chair) at (480) 413-5906.