Piezoresistive properties of single crystalline, polycrystalline, and nanocrystalline n-type 3C-SiC

A detailed experimental study of the influence of crystal quality on the piezoresistive properties of n-type cubic silicon carbide grown by low temperature, low pressure chemical vapor depostion is presented. We have measured the longitudinal gauge factor in single-crystalline, polycrystalline, and nanocrystalline films as a function of conductivity and temperature as well as its directional dependence. In single-crystalline films, the piezoresistive gauge factor is strongly influenced by the layer thickness. The transition from single-crystalline to nanocrystalline 3C-SiC, achieved by a decrease in deposition temperature from 1200 to 1100°C, is shown to result in a change of the corresponding longitudinal piezoresistive gauge factor from −24.8 to positive values of +8 in nominally undoped films. In addition, we observe a drastic change in its dependence on conductivity. We attribute these results to the influence of crystal defects on the strain dependent conductivity.