Self-aligned Scaled Planar N-polar GaN HEMTs with Raised Regrowth

In this paper, we introduce a highly-scaled self-aligned process for N-polar GaN MIS-HEMTs to achieve higher high-frequency performance, using a new structure with a thin unintentional-doped layer (UID) of ohmic regrowth to hold voltage, which is intended to increase breakdown voltage. The process consists of a gate-first process followed by the UID/n+ raised ohmic regrowth via plasma-assisted molecular beam epitaxy (PAMBE). An excellent maximum current of 2.07 A/mm and a low on-resistance of 0.42 Ohm-mm were achieved at V
DS
= 5 V and V
GS
= 1 V for L
G
= 77 nm. A good breakdown voltage of 13 V for lateral-scaled device was measured. Peak transconductance (g
m
) of 430 mS/mm was measured at V
DS
= 3 V. Excellent f
T
·L
G
of 11.1 GHz·μm with a high peak mean electron velocity over 1.5 × 10
⁷
cm/s. This was achieved on commercial epi.