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INDUSTRY ENGINEERED SUBSTRATES


Contributions to GaN-on- diamond development


Figure 8. A comparison of simulations and experimental values for the temperatures for GaN-on- SiC and GaN-on-diamond HEMTs. Experiments involved gate thermometry (left) and micro-Raman (right) techniques. On the left, GaN-on-diamond and GaN-on-SiC HEMTs are compared with equivalent gate-to-gate spacing and dissipation (6.9 W/mm). On the right, the GaN-on-diamond HEMT has a threefold reduction in gate-to-gate spacing relative to the GaN-on-SiC HEMT.


Key milestones in GaN-on-dimaond development:  In 2005, DARPA’s award to Group4 Labs, Inc. of the fi rst seed contract to demonstrate a 10 mm x 10 mm piece of GaN-on-diamond wafer. DARPA would provide instrumental funding later on − via the Near Junction Thermal Transport effort under DARPA’s Thermal Management programme to characterize the thermal benefi ts of the new technology. P1 Diamond and Crystallume Corporation grew the fi rst wafers for the team in 2004 and 2005, respectively.


systems; and it can also enable higher coolant (or device operating) temperatures, because the temperature rise from the coolant to the gate is lower. The higher areal power densities that are possible with the reduced thermal resistance of GaN-on-diamond derive from a shrinking of gate fi nger separation by a factor of three, leading to smaller, cheaper GaN-on-diamond devices.


For the manufacturers of power amplifi er chips, processing three times fewer GaN-on-diamond wafers than GaN-on- SiC variants, while maintaining the same total RF output power, leads to signifi cant reductions in fab costs – assuming that commercial GaN-on-diamond wafers are competitively priced to GaN-on-SiC wafers. And if the GaN-on-diamond wafer price is low enough, then vendors’ power amplifi er savings can be passed on to the system maker, reducing the power amplifi er price per watt.


This is an attractive scenario, showcasing the opportunity for GaN-on-diamond technology to deliver revolutionary advantages for system performance and cost, which can make it the ideal choice for next-generation HEMTs.


 Many people have contributed to the work described in this article: Daniel Francis, Firooz Faili, Frank Lowe, Tim Mollart, Joe Dodson, Daniel Twitchen and Bruce Bolliger from Element Six Technologies; Dubravko Babic from the University of Zagreb; Quentin Diduck from Avogy; Chandra Khandavalli from iMata Technologies; Matthew Tyhach, David Altman and Steve Bernstein from Raytheon Company and Samuel Graham from Georgia Institute of Technology.


The views expressed are those of the author and do not refl ect the offi cial policy or position of the Department of Defense or the US Government.


 In 2006, the fi rst-ever operational transistor on a GaN-on-diamond wafer. The transistors were made by Wright Patterson Air Force Research Labs.


 The US Missile Defense Agency awarding the fi rst of many SBIR programs. TriQuint Semiconductor and Raytheon Company were the fi rst commercial entities to demonstrate operational GaN-on- diamond transistors. The US Navy SBIR program was the fi rst to fund a reliability-related programme with the team in 2009.


 In 2009, Element Six SA – the largest synthetic diamond maker in the world – becoming an instrumental backer of GaN-on- diamond. Element Six subsequently enabled scale-up of the technology after acquiring Group4 Labs in 2013.


Reference M. Tyhach et. al. “Analysis and Characterization of Thermal Transport in GaN HEMTs on SiC and Diamond Substrates”, accepted to GOMACT 2014.


D.C. Dumka et. al. “Electrical and Thermal Performance of AlGaN/GaN HEMTs on Diamond Substrate for RF Applications” in 35th IEEE Compound Semiconductor IC Symposium (CSIC) Oct 13-16 2013, Monterey, CA, Section F.4.


G.D. Via et. al. “Wafer-Scale GaN HEMT Performance Enhancement by Diamond Substrate Integration” in 10th International Conference on Nitride Semiconductors, ICNS- 10, August 25-30, 2013, Washington DC, USA.


F. Ejeckam et. al. “3,000+ Hours Continuous Operation of GaN-on-Diamond HEMTs at 350C Channel Temperature”, Accepted for publication to Semi Therm Conference Mar 9-13, 2014, San Jose, CA.


F. Ejeckam et. al. “GaN-on-Diamond Wafers: A Progress Report”, Accepted for publication at GOMACTech-14, as Paper No. 23.14, April 3, 2014, Charleston, SC.


J. Pomeroy et. al. “Achieving the Best Thermal Performance for GaN-on-Diamond” in 35th IEEE Compound Semiconductor IC Symposium (CSICS) Oct 13-16 2013, Monterey, CA, Section H.4.


46 www.compoundsemiconductor.net October 2014 Distribution Statement A (Approved for Public Release, Distribution Unlimited)


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