Determination of carrier saturation velocity in high-performance InyGa1-yAs/AlxGa1-xAs modulation-doped field-effect transistors (0 ≤ y ≤ 0.2)

We describe a new method for determining the carrier saturation velocity υ
sat
in modulation-doped field-effect transistors (MODFET's). High-performance pseudomorphic In
y
GA
1-y
As/AlGaAs MODFET's (0 ≤ y ≤ 0.20) grown by MBE were tested, and the dependence of υ
sat
on InAs mole fraction y was obtained. It was found that each device with y > 0 had a higher υ
sat
than a conventional GaAs/ AIGaAs MODFET (y = 0). Further, we believe that there is an optimum InAs mole fraction such that υ
sat
is maximized. A pseudomorphic MODFET structure optimizing υ
sat
may also optimize overall device performance.