- 21 January 2005 -

Si-based AlGaN/GaN HEMTs

Picogiga International, a Soitec Group division has achieved technology advancement for RF and microwave components using MBE to enabled the development of the most powerful silicon-based AlGaN/GaN high HEMTs.

Picogiga developed the AlGaN/GaN HEMTs structure with its MBE process for material growth, providing the structures to the research and development group of TriQuint Semiconductor.

Using AlGaN/GaN heterostructures and 0.3m gates to fabricate the devices on Picogiga's Si-based GaN epi material, TriQuint's research facility reports the industry's highest power density to date for a Si-based transistor-continuous wave output power density of 7W/mm at 10GHz without external device cooling.

This equates to power output of 31.5dBm, with a power-added efficiency of 39%. The results confirm the ability of Picogiga's MBE technology to grow GaN-on-silicon, enabling the material advantages of both GaN and Si substrates to be leveraged in a single solution.

"Thanks to improved material growth by Picogiga and TriQuint's optimised process, we achieved high breakdown voltages and good isolation for these devices, which allowed us to operate them at a 40v drain bias," says Deep Dumka, TriQuint senior research engineer.

"Consequently, we have been able to achieve the best possible output power for GaN-on-Si HEMTs. This suggests that GaN-on-silicon has evolved to a level that makes it attractive for implementation in medium-to high-power transistors." The company is now working on optimising the technology reliability and quality.

Picogiga introduced its new family of advanced AlGaN/GaN epitaxial layers on Si substrates in early 2004. "These significant results on our material pave the way for GaN-on-silicon to become a competitive solution for next-generation HEMT power devices," said Jean-Luc Ledys, COO, Picogiga.

AlGaN/GaN HEMTs have experienced remarkable progress in the last few years because of the immense potential for ultra-high-power applications in microwave and millimeter-wave systems.

Until now, sapphire and SiC, have been the materials of choice for demonstrating high-power AlGaN/GaN transistors. The technology, however, continues to face limitations, particularly because of continuing issues with SiC substrate manufacturability, size availability and cost in the more desirable larger diameter format needed for production.

Si substrates are emerging as an attractive alternative for AlGaN/GaN HEMTs. PicoGiga product is currently available in 2", 3" and 4" diameter substrates.