Effects of Uniaxial Compressive Stress on Minority-Carrier Lifetime in Silicon and Germanium

Abstract

Experimental measurements are reported of the effect of mechanical stress on minority-carrier lifetime in germanium and silicon. Lifetime has been measured as a function of temperature and for stress in the 〈111〉, 〈100〉, and 〈011〉 directions at stress levels up to 1010 dyn/cm2. The lifetime changes were found to be reversible, and changes in lifetime of as much as a factor of 3 were observed at stress levels of 1010 dyn/cm2. For all samples investigated, lifetime was observed to increase in n-type material and to decrease in p-type material. A theoretical model has been developed for explaining the effects of mechanical stress on minority-carrier lifetime in germanium and silicon. The model is an extension of the Shockley-Read model to account for stress-induced splitting of the conduction and valence bands plus a possible shift in energy of recombination levels with stress.