摘要
This work presents a comprehensive comparative analysis of two advanced ohmic contact techniques-optimized Ti/Al-based alloy contacts and epitaxial GaN regrowth-to enhance the RF performance of 160 nm T-gate GaN-on-Si HEMTs. For the alloy approach, systematic optimization of the metal stack and barrier recess depth (8 nm) yielded a minimum contact resistance (R c ) of 0.16 Ω*mm. In contrast, the epitaxial regrowth technique demonstrated superior statistical stability and achieved a record-low R c of 0.103 Ω*mm. The impact of contact quality was clearly reflected in the device characteristics; the regrowth HEMT achieved a peak transconductance (g mmax ) of 365 mS/mm, significantly surpassing the 308 mS/mm of the alloy HEMT at a consistent V DS = 5 V. Furthermore, the regrowth device exhibited excellent small-signal performance with a cutoff frequency (f T ) of 60.8 GHz and a maximum oscillation frequency (f max ) of 83 GHz, whereas the alloy device delivered an f T /f max of 26/38.9 GHz. These results demonstrate that while both methods are viable, the highly stable and ultra-low resistance epitaxial regrowth process provides a superior integration pathway for next-generation high-performance RF applications.