Enhanced RF Performance of InAlGaN/GaN HEMTs on Si Substrates with Thin GaN Channel and Quaternary Barrier Optimization

This study demonstrates quaternary In 0.05 Al 0.25 GaN/GaN high electron mobility transistors (HEMTs) fabricated on Si substrates, incorporating a 50 nm thin GaN channel layer. The devices exhibit high carrier density, an impressive On-Off current ratio (∼10 9 ), a high transconductance (G m ) of 400 mS mm −1 , and a wide G m peak width (1.85 V @ 90% G m ), making them well suitable for radio-frequency (RF) applications. Compared to conventional devices utilizing AlGaN and a 500 nm GaN channel as the active layer, the proposed structure achieves a remarkable improvement in On-Off current ratio (enhanced by 10 3 ), a more positive threshold voltage (V th around −1.5 V), and a 15% increase in G m peak width. Additionally, the device with a 200 nm gate length demonstrates a high cutoff frequency ( f t ) of 49.1 GHz and maximum oscillation frequency ( f max ) of 113.8 GHz. These findings underscore the potential of InAlGaN HEMTs with a thin GaN channel layer for high-frequency and RF applications.