SEMICONDUCTOR DEVICE PHYSICS AND DESIGN

410 CHAPTER 8. FIELD EFFECT TRANSISTORS

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VDS = 15 V

InGaN back-barrier HEMT

Standard HEMT

fmax

[GHz

]

fτ[GHz]

Figure 8.37: Effect of the InGaN back-barrier on the power gain of AlGaN/GaN HEMTs. Each
data point represents a different transistor. The variation infτis due to different gate lengths,
which vary from 0.1 to 0.4μmfor the measured devices.

(^0) -14 -12 -10 -8 -6 -4 -2 0
50
100
150
200
250
LG= ~ 0.2 μm
VDS= 7 V
g
(mS/mm)m
VGS (V)
Figure 8.38: Decrease ofgmas the drain current increases (i.e.VGSincreases) in an AlGaN/GaN
HEMT.