Anisotropy in electrical properties of {001} Si/{0112} Al2O3

A detailed investigation of the Hall mobility has been carried out on a series of [inverted lazy s]2-μ-thick n-type {001} Si/{011̄2} Al2O3 films. A specially designed Hall bridge pattern has been used to obtain independent measurements of mobility as a function of current direction in the plane of the film. The data show an anisotropy in the mobility of approximately 9%, with a maximum in mobility occuring along the 〈100〉 Si direction that is parallel to the 〈21̄1̄0〉 Al2O3 direction in the plane of the substrate. This behavior is found to be a consequence, through the piezoresistance effect, of the anisotropic thermal contraction of Al2O3 on cooling from the deposition temperature, which leads to an anisotropic thermally induced stress in the Si.