Self-Aligned N-Polar GaN/InAlN MIS-HEMTs With Record Extrinsic Transconductance of 1105 mS/mm

In this letter, we demonstrate state-of-the-art performance from N-polar GaN/InAlN metal-insulator-semiconductor high-electron mobility transistors (MIS-HEMTs). Self-aligned gate-first process was used for the fabrication of transistors. Graded InGaN and InN contact layers were used to achieve a low ohmic contact resistance of 25 Ω · μm. Excellent dc performance with the highest extrinsic g
_m
of 1105 mS/mm, lowest R
_on
of 0.29 Ω · mm, and maximum current of 2.77 A/mm was achieved for L
_g
= 60 nm. The dc performance was found to scale well with the gate length. The highest f
_T
of 155 GHz was obtained for L
_g
= 30 nm.