Piezoresistance in n-channel inversion layers of silicon films on sapphire

Abstract

The piezoresistance effect in n-channel inversion layers of (001) silicon films on sapphire (SOS) and (001) bulk silicon has been studied at room temperature using metal-oxide-semiconductor field-effect transistors radially arranged on a diaphragm with 36 mm in diameter. The piezoresistance characteristics of inversion layers are markedly different between SOS and bulk silicon. Main features of the experimental results are interpreted on the basis of the deformation potential theory and the surface quantization effect in inversion layers, and it is concluded that the difference between SOS and bulk silicon can be mainly explained by the effect of residual strain in SOS. The piezoresistance coefficients of inversion layers on SOS have been determined experimentally, and have been found that π11≂−π12. In addition, the comparison of the experimental value of π11/π12 with the calculated value is suggested that the transverse mobility of electrons in the valley which have its longitudinal axis of ellipsoid perpendicular to the film surface is smaller as compared with that in the other valleys.