Influence of Oxygen-Vacancy Complex (A Center) on Piezoresistance of n-Type Silicon

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Abstract
Recent experimental studies have shown a unique temperature dependence near room temperature for the piezoresistance of electron‐irradiated n‐type silicon. These reported results do not agree with any existing models for piezoresistance. This paper presents a theoretical effort to explain this effect, along with further experimental work to verify the theory. It is shown that the presence of the oxygen‐vacancy complex (a defect created by electron radiation and commonly referred to as the A center or Si‐B1 center) leads to a temperature‐dependent component of the piezoresistance in addition to that component due to the stress‐induced intervalley transfer of conduction electrons. This additional component is due to a depopulation of the A‐center defect level, and is a direct result of the compensation of the donor atoms by the A‐center acceptor level. In addition to the effect of carrier compensation of piezoresistance by the A center, the model also includes the effects due to relaxation‐time changes with stress along with population transfer. The splitting of the A center defect level with stress is an important part of the model. The model developed is compared to experimental data between 250 and 360°K, and the agreement is found to be quite good.