
129GaN-HEMT Scaling Technologies for High-Frequency
peak value of 400 GHz at a higher V
ds
of 6 V and a similar I
ds
of 0.24 A/mm. Figure
4.22b shows output characteristics and f
T
/f
max
contour plots for 20-nm D-mode HEMT
with an aggressive S-D scaling (L
gs
= L
gd
= 40 nm) (Figure 4.14c). Unlike the unscaled
device, the device showed a continuous increase of f
T
with V
ds
above the V
sat
(~0.5 V)
until reaching a maximum value of 310 GHz at V
ds
=5 V and I
ds
= 0.7 A/mm. A peak
f
max
of 377 GHz was obtained at a similar bias condition. The data demonstrate that
Gate-to-drain distance (nm)
100
L
g
= 20–80 nm
10
1
10
100
Gen-I
Gen-II
Gen-III
Gen-IV