Effect of boundary depletion regions on piezoresistance of polysilicon grains

The polycrystalline semiconductor film consists of various size crystalline grains that have properties of crystalline silicon. The grains are randomly spatially oriented thus decreasing the magnitude of piezoresistance. Depending on the dopant concentration within the grains the depleted regions originated owing to carrier trapping on the grain boundary can have various dimensions. As the carrier concentration within depletion region is lower the resistance and piezoresistance can be higher than in the rest of the grain. Results of the calculation show that deviation of the average parameters such as concentration of free carriers, specific resistivity, piezoresistance coefficient, can be significantly different from that obtained on assumption of uniform free carrier distribution in the crystallite.