RF front-end component maker and foundry services provider TriQuint Semiconductor Inc of Hillsboro, OR, USA has produced what are reckoned to be the industry’s first gallium nitride (GaN) transistors using GaN-on-diamond wafers, which substantially reduce semiconductor temperatures while maintaining high RF performance. The technology could enable new generations of RF amplifiers up to three times smaller or up to three times the power of existing GaN solutions, the firm adds.
Unlocking the true potential of high-efficiency GaN circuits will depend on achievements like those of TriQuint’s advanced research and development program, believes James L. Klein, TriQuint’s VP & general manager for Infrastructure and Defense Products.
Operating temperature largely determines high-performance semiconductor reliability. It is especially critical for GaN devices that are capable of very high power densities. “By increasing the thermal conductivity and reducing device temperature, we are enabling new generations of GaN devices that may be much smaller than today's products,” Klein says. “This gives significant RF design and operational benefits for our commercial and defense customers.”
TriQuint demonstrated its new GaN-on-diamond high-electron-mobility transistors (HEMTs) in conjunction with partners at the UK’s University of Bristol, Group4 Labs and Lockheed Martin under the US Defense Advanced Research Projects Agency’s (DARPA) ‘Near Junction Thermal Transport’ (NJTT) program.
NJTT is the first initiative in DARPA’s new ‘Embedded Cooling’ program, which includes the ICECool Fundamentals and ICECool Applications R&D engagements. NJTT focuses on device thermal resistance ‘near the junction’ of the transistor. Thermal resistance inside device structures can be responsible for more than 50% of normal operational temperature increases, says TriQuint. The firm’s research has shown that GaN RF devices can operate at a much higher power density and in smaller sizes, through its highly effective thermal management techniques.
TriQuint says that its latest development involves the transfer of a semiconductor epitaxial overlay onto a synthetic diamond substrate, providing a high thermal conductivity and low thermal boundary resistance, while preserving critical GaN crystalline layers. This is reckoned to be the first demonstration of the feasibility of GaN-on-diamond HEMT devices. Results to date indicate that TriQuint has achieved the primary NJTT goal of a three-fold improvement in heat dissipation while preserving RF functionality; this supports reducing power amplifier size or increasing output power by a factor of three. Additional fabrication improvements and extensive device testing are underway to optimize the epitaxial layer transfer process and fully characterize the enhancements that can be achieved in the new HEMT devices.
