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Title: Materials physics and device development for improved efficiency of GaN HEMT high power amplifiers.

Abstract

GaN-based microwave power amplifiers have been identified as critical components in Sandia's next generation micro-Synthetic-Aperture-Radar (SAR) operating at X-band and Ku-band (10-18 GHz). To miniaturize SAR, GaN-based amplifiers are necessary to replace bulky traveling wave tubes. Specifically, for micro-SAR development, highly reliable GaN high electron mobility transistors (HEMTs), which have delivered a factor of 10 times improvement in power performance compared to GaAs, need to be developed. Despite the great promise of GaN HEMTs, problems associated with nitride materials growth currently limit gain, linearity, power-added-efficiency, reproducibility, and reliability. These material quality issues are primarily due to heteroepitaxial growth of GaN on lattice mismatched substrates. Because SiC provides the best lattice match and thermal conductivity, SiC is currently the substrate of choice for GaN-based microwave amplifiers. Obviously for GaN-based HEMTs to fully realize their tremendous promise, several challenges related to GaN heteroepitaxy on SiC must be solved. For this LDRD, we conducted a concerted effort to resolve materials issues through in-depth research on GaN/AlGaN growth on SiC. Repeatable growth processes were developed which enabled basic studies of these device layers as well as full fabrication of microwave amplifiers. Detailed studies of the GaN and AlGaN growth of SiC were conducted andmore » techniques to measure the structural and electrical properties of the layers were developed. Problems that limit device performance were investigated, including electron traps, dislocations, the quality of semi-insulating GaN, the GaN/AlGaN interface roughness, and surface pinning of the AlGaN gate. Surface charge was reduced by developing silicon nitride passivation. Constant feedback between material properties, physical understanding, and device performance enabled rapid progress which eventually led to the successful fabrication of state of the art HEMT transistors and amplifiers.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Laboratories
Sponsoring Org.:
USDOE
OSTI Identifier:
883465
Report Number(s):
SAND2005-7587
TRN: US200614%%711
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AMPLIFIERS; DISLOCATIONS; EFFICIENCY; ELECTRICAL PROPERTIES; ELECTRON MOBILITY; ELECTRONS; FABRICATION; FEEDBACK; MICROWAVE AMPLIFIERS; NITRIDES; PASSIVATION; PHYSICS; POWER AMPLIFIERS; RELIABILITY; ROUGHNESS; SILICON NITRIDES; SUBSTRATES; THERMAL CONDUCTIVITY; TRANSISTORS; Synthetic Aperture Radar.; Gallium nitride-Electric properties.; Power amplifiers-Design and construction.

Citation Formats

Kurtz, Steven Ross, Follstaedt, David Martin, Wright, Alan Francis, Baca, Albert G., Briggs, Ronald D., Provencio, Paula Polyak, Missert, Nancy A., Allerman, Andrew Alan, Marsh, Phil F., Koleske, Daniel David, Lee, Stephen Roger, Shul, Randy John, Seager, Carleton Hoover, and Tigges, Christopher P. Materials physics and device development for improved efficiency of GaN HEMT high power amplifiers.. United States: N. p., 2005. Web. doi:10.2172/883465.
Kurtz, Steven Ross, Follstaedt, David Martin, Wright, Alan Francis, Baca, Albert G., Briggs, Ronald D., Provencio, Paula Polyak, Missert, Nancy A., Allerman, Andrew Alan, Marsh, Phil F., Koleske, Daniel David, Lee, Stephen Roger, Shul, Randy John, Seager, Carleton Hoover, & Tigges, Christopher P. Materials physics and device development for improved efficiency of GaN HEMT high power amplifiers.. United States. doi:10.2172/883465.
Kurtz, Steven Ross, Follstaedt, David Martin, Wright, Alan Francis, Baca, Albert G., Briggs, Ronald D., Provencio, Paula Polyak, Missert, Nancy A., Allerman, Andrew Alan, Marsh, Phil F., Koleske, Daniel David, Lee, Stephen Roger, Shul, Randy John, Seager, Carleton Hoover, and Tigges, Christopher P. Thu . "Materials physics and device development for improved efficiency of GaN HEMT high power amplifiers.". United States. doi:10.2172/883465. https://www.osti.gov/servlets/purl/883465.
@article{osti_883465,
title = {Materials physics and device development for improved efficiency of GaN HEMT high power amplifiers.},
author = {Kurtz, Steven Ross and Follstaedt, David Martin and Wright, Alan Francis and Baca, Albert G. and Briggs, Ronald D. and Provencio, Paula Polyak and Missert, Nancy A. and Allerman, Andrew Alan and Marsh, Phil F. and Koleske, Daniel David and Lee, Stephen Roger and Shul, Randy John and Seager, Carleton Hoover and Tigges, Christopher P.},
abstractNote = {GaN-based microwave power amplifiers have been identified as critical components in Sandia's next generation micro-Synthetic-Aperture-Radar (SAR) operating at X-band and Ku-band (10-18 GHz). To miniaturize SAR, GaN-based amplifiers are necessary to replace bulky traveling wave tubes. Specifically, for micro-SAR development, highly reliable GaN high electron mobility transistors (HEMTs), which have delivered a factor of 10 times improvement in power performance compared to GaAs, need to be developed. Despite the great promise of GaN HEMTs, problems associated with nitride materials growth currently limit gain, linearity, power-added-efficiency, reproducibility, and reliability. These material quality issues are primarily due to heteroepitaxial growth of GaN on lattice mismatched substrates. Because SiC provides the best lattice match and thermal conductivity, SiC is currently the substrate of choice for GaN-based microwave amplifiers. Obviously for GaN-based HEMTs to fully realize their tremendous promise, several challenges related to GaN heteroepitaxy on SiC must be solved. For this LDRD, we conducted a concerted effort to resolve materials issues through in-depth research on GaN/AlGaN growth on SiC. Repeatable growth processes were developed which enabled basic studies of these device layers as well as full fabrication of microwave amplifiers. Detailed studies of the GaN and AlGaN growth of SiC were conducted and techniques to measure the structural and electrical properties of the layers were developed. Problems that limit device performance were investigated, including electron traps, dislocations, the quality of semi-insulating GaN, the GaN/AlGaN interface roughness, and surface pinning of the AlGaN gate. Surface charge was reduced by developing silicon nitride passivation. Constant feedback between material properties, physical understanding, and device performance enabled rapid progress which eventually led to the successful fabrication of state of the art HEMT transistors and amplifiers.},
doi = {10.2172/883465},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Dec 01 00:00:00 EST 2005},
month = {Thu Dec 01 00:00:00 EST 2005}
}

Technical Report:

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  • The Fermi Lab PIP II (formerly Project X) accelerator will require the generation of over a megawatt of radio-frequency (RF) power at 325 and 650 MHz. This Phase-II SBIR grant developed techniques to generate this RF power efficienly. The basis of this approach is a system comprising high-efficiency RF power amplifiers, high-efficiency class-S modulators to maintain efficiency at all power levels, and low-loss power combiners. A digital signal processor adjusts signal parameters to obtain the maximum efficiency while producing a signal of the desired amplitude and phase. Components of 4-kW prototypes were designed, assembled, and tested. The 500-W modules producemore » signals at 325 MHz with an overall efficiency of 83 percent and signals at 650 MHz with an overall efficiency of 79 percent. This efficiency is nearly double that available from conventional techniques, which makes it possible to cut the power consumption nearly in half. The system is designed to be scalable to the multi-kilowatt level and can be adapted to other DoE applications.« less
  • This Phase-I SBIR grant investigated techniques for high-efficiency power amplification for DoE particle accelerators such as Project X that operate at 325 and 650 MHz. The recommended system achieves high efficiency, high reliability, and hot-swap capability by integrating class-F power amplifiers, class-S modulators, power combiners, and a digital signal processor. Experimental evaluations demonstrate the production of 120 W per transistor with overall efficiencies from 86 percent at 325 MHz and 80 percent at 650 MHz.