Piezoresistive Strain Gages and Transducer Elements

The piezoresistive effect, the change in resistivity caused by mechanical stress, is large enough in semiconductors for use in strain gages and other transducer elements. This paper reviews the piezoresistive effect in semiconductors having diamond or zincblende crystal structures and discusses applications. Definitions and typical values are given for the important material properties such as stress sensitivity, strain sensitivity, temperature dependence of sensitivity, and effect of crystal orientation. In addition, new information is given on piezoresistive properties of diffused layers on semiconductors, and diffused sensing elements of several types are analyzed. The advantages of increased design flexibility and improved sensitivity over uniformly doped gages are shown.