Enhancement Mode β-(AlxGa1-x)2O3/Ga2O3 Heterostructure FET (HFET) With High Transconductance and Cutoff Frequency

This letter reports
$\beta $
-(Al
_x
Ga
_1-x
)
₂
O
₃
/Ga
₂
O
₃
(AlGaO/GaO) heterostructure FETs (HFETs) with significant improvement of peak transconductance (g
_m
), current and power gain cutoff frequencies. A modulation doping scheme is used to form a two dimensional electron gas in AlGaO/GaO heterostructures. Highly scaled transistors (gate lengths of 160–200 nm) were fabricated on these wafers with source/drain regrowth, scaled source access lengths and Pt Schottky gates. The fabricated HFETs show an enhancement-mode operation with high transconductance and a peak current density of 74 mA/mm. Small signal measurements show a peak current gain cut off frequency (f
_T
) and power gain cutoff frequency (f
_max
) of 30 and 37 GHz respectively at 10 V drain voltage. While the cutoff frequencies are highest to date, they are limited by high source resistance at the regrowth interface. We observed a moderate off state breakdown at V
_GS
= −2 V, limited by gate leakage and Schottky gate breakdown with an average field strength of 1.35 MV/cm. The f
_T
.L
_G
product 4.8 GHz-
${\mu }\text{m}$
reported for this device is higher than any other current generation
$\beta $
-Ga
₂
O
₃
transistors which paves the way for future RF device applications.