  We probe electro-mechanical properties of InAs nanowire (diameter ~ 100 nm)
resonators where the suspended nanowire (NW) is also the active channel of a
field effect transistor (FET). We observe and explain the non-monotonic
dispersion of the resonant frequency with DC gate voltage (VgDC). The effect of
electronic screening on the properties of the resonator can be seen in the
amplitude. We observe the mixing of mechanical modes with VgDC. We also
experimentally probe and quantitatively explain the hysteretic non-linear
properties, as a function of VgDC, of the resonator using the Duffing equation.
