HRL claims high frequency GaN breakthrough
by Andy Extance
The development and deployment of broad bandwidth wireless links has received a significant boost, with research laboratory HRL unveiling a new GaN-based power amplifier for high frequency applications.
“Our product development roadmap calls for a roll-out in late 2007,” HRL told compoundsemiconductor.net. “In the near term (2008-2009), [HRL] foresee market sizes as large as 10,000-100,000 chips/year.”
As well as being the first GaN MMIC amplifier to target the specific “W-band” frequency range (75 to 110 GHz), the component boasts a power density of 2.1 W/mm, as compared to just 0.26 W/mm in the equivalent InP chip that HRL previously considered to be the “state of the art”.
These high-performance chips were made using plasma-assisted MBE to grow heavily doped GaN and AlGaN cap layers, and depositing low resistance ohmic contacts.
Also key to the realization of the chip was an AlGaN/GaN/AlGaN double heterojunction that reduced short-junction effects, and development of means to dry-etch slot vias.
“Until very recently GaN-based devices were not seriously considered for power applications at frequencies that are higher than 50 GHz, due to difficulty with material processing and due to the lack of a device structure suitable for high frequency applications,” explained HRL.
The output frequencies encompassed by the new device includes the three E-band spectrum segments approved in the US for gigabit-rate wireless links, and this innovation could translate to a three-fold increase in operating range for HRL's broadband communication protocol.
HRL suggests that the level of power amplification achieved in the GaN MMIC will allow the development of cost-effective wireless data transmission at 10 Gb/s, and increase the operating range of radar systems by 70%.
Due to the smaller chip size per Watt emitted, these chips also offer higher efficiency at high power levels, leading to reduced cooling requirements and lower costs.
The improvements that the GaN MMICs could bring to millimeter-wave broadband wireless communications strengthens the case for this being the next technology in high speed data transfer, beyond the avoidance of logistical issues associated with installing FTTx infrastructure.
By showing that fabrication concerns may be overcome, HRL may have opened the door for further high power devices in this range based on GaN.
• Gigabeam, the US company that specializes in gigabit wireless communication, has agreed a contract with the Ministry of the Interior of the Kingdom of Bahrain for a high-speed network linking government buildings across the country.
Under the terms of the contract, Gigabeam will receive $1.37M to work with Motorola and Cisco in provision of the backbone infrastructure.
Author
Andy Extance is a reporter at compoundsemiconductor.net.
