Gallium Nitride Electronics Watt is the limit

							                                       “Gallium Nitride Electronics: Watt is the limit?”

                                             Thursday, June 24, 2004 (10:30 a.m.)
                                                    (Refreshments @11:30)
                                          Electrical Engineering Building, Room 317

                                                      Dr. Umesh K. Mishra
                                        Electrical and Computer Engineering Department
                                            University of California @ Santa Barbara
Gallium Nitride and its alloys with Indium Nitride and Aluminum Nitride are being researched increasingly broadly because of
applications spanning both the optical (UV emission/detection, blue lasers and blue green and white lighting) to the electronic
(microwave power amplifiers and switching power supplies). Though the former has driven the market to date, a large market in the
latter is ready for launch. This talk will discuss the devices being developed for the electronic applications.

The dominant electronic device, the GaN-based HEMT, is being developed for both microwave and power switching applications.
The first microwave power performance of 1.1 W/mm at 2GHz was demonstrated by 1995 and since then the progress has been
meteoric getting boosts from critical technological developments, namely improved quality of the semi-insulating buffer passivation
as a means of eliminating the DC to RF dispersion and SiC as a thermally conductive substrate. The use of field plates for microwave
devices have led to exceptional power densities {32W/mm on SiC and 12W/mm on Sapphire. NEC and Fujitsu have demonstrated
power at 2GHz approaching 200W from scaled devices. Newly developed technologies in gate recess etching and ion implantation for
ohmic contacts promise to enhance the reproducibility and yield of these devices further.

There is an effort to harness the materials properties of GaN for applications in high frequency, compact power supplies This
primarily called for transistors with a breakdown voltage of 1kV and a current handling capability of 1A to 10A. Progress in this area
will be presented. Thjough fundamentally attractive Heterojunction Bipolar Transistors dominant problems in the development remain
the poor electronic properties of p-type GaN and leakage through p-n junctions and etched surfaces.

Lastly, the polarization inherent in this material system allows for unique device structures. The POLFET is based on modulating a
three dimensional electron slab created by grading the polarization in the system resulting in a MESFET with no doping. Also the high
polarization allows one to make schottky diodes with thin AlGaN inserts, which allow a reduction in the forward turn-on voltage of
diodes while retaining a large barrier to reverse currents. This has intriguing applications of a GaN based device for low power
switching applications. The talk will conclude with some highly dependable predictions.

Short Bio:

Umesh K. Mishra received the Ph.D. degree from Cornell University, Ithaca, NY, in 1984, the M.S. from Lehigh University,
Bethlehem, PA in 1980, and the B.Tech. from the Indian Institute of Technology (IIT) Kanpur, India in 1979, all in Electrical
Engineering. He has worked in various laboratory and academic institutions, including Hughes Research Laboratories, Malibu, CA,
University of Michigan at Ann Arbor, and General Electric, Syracuse, NY, where he has made major contributions to the development
of AlInAs-GaInAs HEMT’s and HBT’s. He is now a Professor and the Department Chair at the Department of Electrical and
Computer Engineering, University of California at Santa Barbara. His current research interests are in oxide based III-V electronics
and III-V nitride electronics and opto-electronics. Dr. Mishra was a co-recipient of the Hyland Patent Award given by Hughes
Aircraft, and the Young Scientist Award presented at the International Symposium on GaAs and Related Compounds. He has authored
or co-authored over 450 papers in technical journals and conferences and holds 9 patents.

                                                        SPONSORED BY:
                      Birck Nanotechnology Center, The NASA Institute for Nanoelectronics and Computing,
                 The Network for Computational Nanotechnology, Department of Chemistry, Department of Physics,
         School of Chemical Engineering, School of Electrical and Computer Engineering, School of Mechanical Engineering


             Participants eager to present their research should contact the organizer of this seminar series at
                                                     gba@purdue.edu.