Effect of Mechanical Stress on <i>p-n</i> Junction Device Characteristics

TLDR

The study develops a theoretical model to predict how mechanical stress alters the electrical behavior of Ge and Si p‑n junction devices. The model links stress‑induced band‑structure changes to minority carrier densities, derives stress‑dependent I‑V equations for diodes and transistors, and demonstrates these effects with examples of localized junction stress. The results show that minority carrier densities and device currents vary strongly with stress type—anisotropic stresses causing larger changes—and that currents can shift by orders of magnitude for stresses above 10¹⁰ dyn/cm², in good agreement with experimental data.

Abstract

A theoretical model is developed for the effect of mechanical stress on the electrical characteristics of Ge and Si p-n junction devices. This model is based upon the stress-induced variations in energy band structure and their effect on minority carrier densities. The changes in minority carrier densities are shown to depend upon the type of stress applied, with anisotropic stresses causing larger changes than hydrostatic stresses. From the calculated dependence of minority carrier densities upon stress, the equations are developed for the current—voltage characteristics of diodes and transistors under stress. Following the general analysis several examples are given in which stress is applied to a small section of a junction in a diode or transistor. The results show that at stress levels greater than 1010 dyn/cm2, the device currents can change by several orders of magnitude when stress levels are changed by a factor of 2. The theory is compared with published experimental data and found to be in good agreement.