Determination of the mobility profile in silicon-on-sapphire material using the “fat” FET principle

Using a field effect transistor (FET) structure with a Schottky gate, the mobility profile in a silicon layer is calculated from capacitance and conductance measurements. The measurements require ordinary laboratory instruments only. A short theory is presented, followed by experimental values for silicon on sapphire (SOS) material. The results show a sharp decrease in mobility at the defect rich layer close to the sapphire and close to the silicide gate junction. A maximum mobility of 490 cm 2 /Vs for electrons and 190 cm 2 /Vs for holes was obtained for a position roughly in the middle of the silicon layer.