Effects of Uniaxial and Inhomogeneous Stress in Germanium and Silicon p-n Junctions

Abstract

Results are reported of experimental investigations of the effect of uniaxial compression up to 1.8×10¹⁰ dyn‐cm⁻² on grown Ge and Si junctions and of strongly inhomogeneous stress applied directly to the junctions. In Ge, agreement in sign and in magnitude within factors of about two and ten, respectively, was obtained between the currents induced by uniaxial stress in 〈111〉 and 〈110〉 directions and those predicted by a bandgap mechanism. No significant effect of uniaxial stress up to about 1.5×10¹⁰ dyn‐cm⁻² on the reverse‐bias current was found in Si (111) junctions; however, changes in breakdown voltage and of forward‐bias current were observed. The presence of crystal defects is shown to enhance sensitivity to uniaxial stress and, in Si, was found to be a necessary condition for an effect on the reverse‐bias current. Defects introduced by strongly localized stress appear to play a similar role to those active in uniaxial stress effects. It is concluded that the bandgap mechanism proposed by Wortman et al. applies both in Ge and in Si, but that it is partially masked in the latter by stress‐independent generation‐recombination currents. The plausibility of a generation‐recombination mechanism, possibly such as that proposed by Bernard et al., as an underlying cause of the effects of high localized stress is discussed.