The influence of crystal quality on the piezoresistive effect of β-SiC between RT and 450°C measured by using microstructures

The gauge factor of /spl beta/-SiC was measured for dependence on the crystal quality, the doping type and the doping level between room temperature and 400/spl deg/C. A new measurement method using micromachined SiC bridge structures together with a piezoelectric micromanipulator set-up was applied to make non-isolated SiC films on silicon accessable to measurements. The most intriguing result is that the gauge factor of n-doped mono-crystalline /spl beta/-SiC is negative, whereas that of poly-crystalline material is positive. Considering the dependence of the gauge factor on the temperature, the crystal orientation and the doping type this could be explained by the greater influence of grain boundaries in the case of polycrystalline wide bandgap materials compared to silicon.