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.

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The epitaxial growth of Hg1−xCdxTe has been investigated by means of a technique in which the source and substrate are close spaced, and both under isothermal conditions and with a temperature gradient between the source and substrate. The effect of excess mercury pressure in the ampoule on the growth rate and the compositional profile within the isothermally grown epitaxial layers has been investigated in detail. A simple isothermal process is described for making epitaxial layers having a controlled surface alloy composition. The presence of a temperature gradient between the source and the substrate significantly enhances the deposition rate and results in a linear relation between the layer thickness and deposition time. The electrical and optical properties of the isothermally grown epitaxial layers are discussed along with the results of photoconductivity measurements on layers having surface composition of x=0.20 and x=0.25.

The temperature and compositional dependences of the energy gap are determined for the alloy semiconductor mercury-cadmium telluride (Hg1−xCdxTe). The cutoff wavelength was measured on photoconductive and photovoltaic infrared detectors where 0.17<x<0.60 over a temperature range 20<T< 300°K. Spectral response curves are shown to indicate the precision of the method. The temperature and compositional dependences of the energy gap are shown and the empirical expression Eg (eV) =1.59x−0.25+5.233(10−4)T(1−2.08x)+0.327x3is deduced.

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