ORIGIN OF THE SHEAR PIEZORESISTANCE COEFFICIENT-PI-44 OF N-TYPE SILICON

It is shown that the origin of the shear piezoresistance (PR) coefficient pi-44 of n-type silicon is a stress-induced effective-mass change of individual valleys rather than the stress-induced intervalley electron transfer, which has long been believed to be the dominant source of PR in many-valley semiconductors. An orthorhomic stress destorys the rotational symmetry of the ellipsoidal valleys and induces large effective-mass changes due to the special character of the conduction-band edge of silicon. The effective-mass anisotropy then leads to a transverse voltage when the current is along [100]. This mechanism predicts a sign and a magnitude of pi-44 for n-type Si that are consistent with experiments hitherto known.