Piezoresistivity of Epitaxial SiGe

Piezoresistivity of B- and P-doped epitaxial Si1-xGex (x = 10%–30%) is investigated to assess its application potential for thin film strain sensors. The gauge factor (GF) is calculated based on the change in resistivity to the externally induced compressive uniaxial strain along the current flow direction. In the case of B-doped SiGe, the resistivity decreases under the induced compressive strain which may be related to hole mobility enhancement, while no influence on the resistivity of the P-doped SiGe. A significant increase in the GF is observed by lowering B concentration. At the same B concentration, slightly higher GF is observed for higher Ge content. Moreover, the GF is slightly improved by lowering the SiGe growth temperature, which may be related to improved crystallinity indicated by capacitance-voltage characteristics of metal-oxide-semiconductor structure using the epitaxial SiGe on Si. These results suggest that the low-doped p-type SiGe deposited at low temperature has reasonable GF and can potentially be applied in strain sensors.