High-Performance AlN/GaN MISHEMTs on Si With In-Situ SiN Enhanced Ohmic Contacts for Mobile mm-Wave Front-End Applications

Abstract

In this letter, we demonstrated an AlN/GaN metal-insulator-semiconductor high electron mobility transistor (MISHEMT) on a Si substrate with in-situ SiN as gate dielectric with excellent mm-wave performance at low supply voltages. Benefited from the thin in-situ SiN, a low ohmic contact resistance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R} _{C}$ </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">$0.2 \sf {\Omega } \cdot \text {mm}$ </tex-math></inline-formula> was obtained. The device with a T-shape gate featuring 80 nm gate 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">${L} _{G}$ </tex-math></inline-formula> ) and 620 nm total gate metal thickness 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">${I} _{D}$ </tex-math></inline-formula> ) of 1.95 A/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 500 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">${f} _{T}/{f} _{\text {max}}$ </tex-math></inline-formula> ) of 165/255 GHz. To the best of our knowledge, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f} _{T}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f} _{\text {max}}$ </tex-math></inline-formula> are the highest among the reported AlN/GaN transistors on Si substrates. 28 GHz load-pull measurements at low drain voltages of 3.5/5/6 V show maximum output power densities ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P} _{\text {out},\text {max}}$ </tex-math></inline-formula> ) of 0.36/0.73/1.04 W/mm and peak power-added efficiencies (PAE) of 40%/42%/43%, respectively. These excellent results show that AlN/GaN HEMTs on Si have a great potential for power amplifiers (PAs) in mobile mm-wave front-end applications.