Analysis of piezoresistance in p-type silicon for mechanical sensors

Abstract

Typical p-type silicon mechanical sensors are designed to operate under temperature range from /spl sim/173 K to /spl sim/373 K and subjected to stress less than /spl sim/100 MPa. The operation range is mainly restricted by the electrical and mechanical properties of silicon. The authors derived an approximate piezoresistance equation valid for typical operation range of the p-type silicon mechanical sensors, from valence band model of Bir and Pikus taking into account the spin-orbit interaction. The piezoresistance in p-type silicon was analyzed based on hole transfer and conduction mass shift due to stress. These mechanisms were introduced by Suzuki et al. [1984] to interpret piezoresistance in p-type silicon, based on the valence band equation in the vicinity of k=0. Under the typical operation range for p-type silicon mechanical sensors, holes are located where the value of k is relatively large, i.e., off k=0 and degenerate band split due to stress is incomplete. The hole behavior in the valence band was compatible with the typical operation range for p-type silicon mechanical sensors.