Stress-dependent hole effective masses and piezoresistive properties of p-type monocrystalline and polycrystalline silicon

Piezoresistive effects of p-type polycrystalline silicon underline that longitudinal and transversal piezoresistive properties in monocrystalline silicon do not have the same physical origin, which is not accounted for in current models. This difference is highlighted by the study of the mechanical stress effect on the valence band, which shows that piezoresistive properties of p-type monocrystalline silicon can he explained in terms of both hole transfer between heavy-and light-hole valence bands and stress-dependent hole effective masses. The quantification of these phenomena points out that longitudinal piezoresistive properties are mainly due to the hole transfer, whereas transversal ones an mainly attributed to the effective mass change effects. This enables one to model p-type polycrystalline silicon piezoresistivity, in particular the sign change of the transversal gauge factor at high doping level. [S0163-1829(98)01615-4].