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The piezoresistive properties of n- and p-type layers formed by the diffusion of impurities into silicon have been investigated. The values of the three piezoresistance coefficients and the temperature dependence of the large coefficients have been measured on layers having surface concentration values from 1018 to 1021 cm−3. The piezoresistance effect in p-type diffused layers follows qualitatively the behavior expected in a degenerate semiconductor. n-type layers having high surface concentration values show a change in the symmetry of the piezoresistance effect at room temperature and a decrease in the coefficient π11 at lower temperatures. A discussion of the piezoresistance effect in diffused layers and its relation to the piezoresistance effect in uniformly doped material is also given.

The properties of a pressure transducer consisting of a single-crystal silicon diaphragm having stress-sensitive piezoresistive regions formed by the localized diffusion of impurities have been theoretically and experimentally investigated. The longitudinal and transverse piezoresistance effects are discussed and the results are applied to the stress pattern of a deformed diaphragm. The conditions under which the stress in the diaphragm varies linearly with applied pressure are discussed and good agreement between the predicted and measured sensitivity is found in both the linear and nonlinear cases.

Measurements have been made of the temperature dependences of the electrical resistivity and Hall coefficient in samples of n- and p-type silicon having impurity concentrations in the 1018 to 1020 cm−3 range. The resistivity data extend from 4° to 900°K, and the Hall data from 4° to 300°K. The results exhibit two noteworthy features: viz., (1) a hump or maximum in the resistivity vs temperature curves at or slightly below the degeneracy temperature in each sample, which is most pronounced in the least heavily doped samples and gradually fades out as the impurity concentration increases, and (2) an extension of the positive dependence of resistivity on temperature below the hump or degeneracy temperature to surprisingly low temperatures in each sample.

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