Multi-Gate Finger Microwave GaN HEMTs on Si Substrates With Individual Source Vias

In this letter, we fabricated multi-gate finger GaN microwave high electron mobility transistors (HEMTs) on a 6” silicon substrate with individual source vias (ISVs) for the interconnect of the source pads. Compared to the air bridges, the technology of ISVs shows lower parasitic capacitances, and potentially a higher volume fabrication yield. The device with a T-shape gate with a foot length <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{\text {g}}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.5~\mu $ </tex-math></inline-formula> m and width of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${4}\times {100}~\mu $ </tex-math></inline-formula> m shows a maximum drain current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {dmax}}$ </tex-math></inline-formula>) of 600 mA/mm, a peak transconductance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${g}_{\text {mmax}}$ </tex-math></inline-formula>) of 200 mS/mm, and a cut-off frequency/a maximum oscillation frequency (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}_{\text {T}}/ {f}_{\max }$ </tex-math></inline-formula>) of 19/27 GHz. Large-signal load-pull measurement at a frequency of PW (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$100~\mu $ </tex-math></inline-formula> s pulse width and 10 ms pulse period) 3.5 GHz and a drain voltage of 35 V showed a saturated output power density (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {sat}}$ </tex-math></inline-formula>) of 4.8 W/mm, and a peak power-added efficiency (PAE) of 73%, respectively. These results are similar to the performance of the device with source pads interconnected by air bridges and demonstrate the great potential for the technology of ISVs in the application of large size-wafer GaN-on-Si microwave devices.