Texas State University validates Atomera MST results
Researchers at Texas State University (TXST) in collaboration with semiconductor materials company Atomera have pioneered a novel manufacturing approach that tackles a longstanding weakness in GaN-on-Si semiconductors.
Their tests have now confirmed more than a tenfold reduction in parasitic interface charge versus conventional GaN-on-SI structures using Atomera's Mears Silicon Technology (MST). MST introduces a thin, oxygen-modified layer near the surface of the silicon wafer, creating a more favourable platform for GaN growth.
The researchers say the technology could lower the cost and improve the performance of the RF semiconductors, bringing higher linearity than has typically been possible.
“GaN-on-silicon has historically limited RF performance in terms of both radio frequency and device efficiency,” said Edwin L. Piner, professor and director of the university's Center for Research, Entrepreneurship and Science and Technology (CREST), who led the research. “The Texas State-Atomera collaboration has addressed this limitation, thereby enabling devices that use less energy and are capable of being developed for advanced market applications.”
While GaN-based devices built on SiC substrates offer excellent performance, their high manufacturing costs have limited widespread adoption. Silicon substrates provide a lower-cost alternative, but unwanted electrical effects have traditionally prevented them from matching the performance of their SiC counterparts.
To solve the problem, the researchers tested Atomera's MST, which acts as a barrier, stopping gallium and aluminum atoms from drifting into the silicon as the semiconductor is built. Without the barrier, the stray atoms can create an unwanted path for electrical current and cause signal loss, distortion, and lower efficiency in high-frequency devices.
Piner (pictured above) and his team grew and tested semiconductor structures made both with and without the MST diffusion barrier.
Their results showed that MST reduced interfacial charge (unwanted electrical charge that builds up where different materials meet) over tenfold compared with conventional GaN-on-Si structures. The researchers also found that far fewer impurities migrated into the silicon substrate, helping prevent the formation of a parasitic channel, an unwanted pathway that can interfere with device performance.
The improvement has significant implications for RF performance. By reducing parasitic charge and related losses, the technology gives low-cost GaN-on-silicon devices much higher linearity than has typically been possible. Improved linearity can lead to better signal quality and more efficiency in communications and sensing systems.
“Dr. Piner’s team has developed a world-class RF GaN-on-Si baseline, making them an ideal collaborator to evaluate the impact of our MST technology," said Robert Mears, founder and CTO at Atomera. "By combining TXST’s baseline GaN stack on our MST silicon wafers, we have been able to demonstrate the low RF losses, high linearity and ultra-low crosstalk performance characteristics that RF designers are looking for in developing next-generation wireless networks."
“GaN devices are widely used in cellular networks, satellite communications, and defence radar systems,” Piner said. “In military missile tracking systems, performance improvements can translate into systems that are ten times more effective in defensive capabilities.”
