Evaluation of beta -SiC for sensors

The sensor properties of n-type beta -SiC, namely the gauge factor (GF) and temperature coefficient of resistivity (TCR), are reported over a wide range of temperatures. The maximum gauge factor observed was -31.8, which decreases to half its value over the temperature range 25-450 degrees C. Unintentionally doped SiC has a constant TCR of 0.72%/ degrees C over the range 25-800 degrees C and exhibits full impurity ionization at room temperature. Low-resistivity, nitrogen doped SiC is fully ionized at 250 degrees C, above which the resistance increases nonlinearly with temperature. It is shown that n-type beta -SiC has a large strain sensitivity, making it a potentially useful high-temperature sensing element. The piezoresistive properties of SiC can be explained simply by intervalley electron transfer.<
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