Cornell University has unveiled a significant breakthrough in next-generation semiconductor engineering with the development of a new high-electron-mobility transistor (XHEMT) built on single-crystal aluminium nitride (AlN) substrates. Designed for high-power, high-frequency wireless applications, the new architecture offers major improvements in thermal performance, defect reduction, and long-term reliability while addressing growing supply chain constraints around gallium. 

A New Device Structure Built for Future Wireless Networks 

The Cornell research team engineered an ultra-thin pseudomorphic gallium nitride (GaN) channel layer, placed between two AlN layers and grown on a bulk single-crystal AlN substrate. The material’s ultra wide band gap and exceptionally low defect density allow the transistor to withstand higher temperatures and voltages with reduced electrical losses. 

• 5G and emerging 6G RF power amplifiers 

• Advanced radar systems 

• High-frequency wireless communication networks 

According to researchers, the AlN substrate provides superior thermal conductivity, enabling significantly cooler operation under high power. This directly enhances device lifespan and performance consistency, especially in demanding RF environments. 

Ultra-Low Defects: A Million-Fold Improvement 

One of the most notable outcomes of the new architecture is the drastic reduction in crystalline defects. Traditional GaN-based devices grown on silicon, silicon carbide or sapphire often suffer from defect propagation throughout the device. In contrast, Cornell’s lattice-matched AlN-based design results in: 

• Nearly one million times fewer defects 

• Cleaner epitaxial layers 

• Higher reliability at elevated power levels 

The research team believes this structural purity will provide a strong competitive advantage in future iterations of high-performance RF devices. 

Strategic Advantage: Reducing Gallium Dependence 

As the global demand for GaN continues to rise across automotive, telecom and power electronics, gallium supply chain vulnerabilities have become a national concern. With over 90% of gallium produced outside the U.S., export restrictions have strained availability. 

Cornell’s approach dramatically reduces gallium consumption using only minimal quantities in the channel layer offering a pathway toward: 

• Reduced material dependency 

• Greater U.S. manufacturing resilience 

• More secure semiconductor supply chains 

Industry-Scale Progress and Collaboration 

The team recently demonstrated wafer-scale growth of the XHEMT structure on 3-inch AlN wafers, a milestone featured in APL Materials and supported by the Northeast Regional Defense Technology Hub (NORDTECH). 

The research involved a multi-disciplinary collaboration across Cornell’s engineering departments, with support from: 

• Army Research Office (ARO) 

• Defense Advanced Research Projects Agency (DARPA) 

• Asahi-Kasei Corporation 

• Cornell Nano Scale Facility 

• Cornell Center for Materials Research 

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