  In this paper we critically review and compare experimental methods, based on
the Lundstrom model, to extract the channel backscattering ratio in nano
MOSFETs. Basically two experimental methods are currently used, the most common
of them is based on the measurement of the saturation drain current at
different temperatures. We show that this method is affected by very poor
assumptions and that the extracted backscattering ratio strongly underestimates
its actual value posing particular attention to the backscattering actually
extracted in nano devices. The second method is based on the direct measurement
of the inversion charge by CV characteristics and gets closer to the physics of
the backscattering model. We show, through measurements in high mobility
p-germanium devices, how the temperature based method gives the same result of
the CV based method once that its approximations are removed. Moreover we show
that the CV based method uses a number of approximations which are partially
inconsistent with the model. In particular we show, with the aid of 2D quantum
corrected device simulations, that the value of the barrier lowering obtained
through the CV based method is totally inconsistent with the barrier lowering
used to correct the inversion charge and that the extracted saturation
inversion charge is underestimated.
