Characterization of n-type beta -SiC as a piezoresistor

SiC is currently being investigated for device applications involving high temperatures. The properties of n-type beta -SiC relevant to piezoresistive devices, namely the gauge factor (GF) and temperature coefficient of resistivity (TCR), are characterized for several doping levels. The maximum gauge factor observed was -31.8 for unintentionally doped (10/sup 16/-10/sup 17//cm/sup 3/) material. This gauge factor decreases with temperature to approximately half its room-temperature value at 450 degrees C. Unintentionally doped SiC has a roughly constant TCR of 0.72%/ degrees C over the range 25-800 degrees C and exhibits full impurity ionization at room temperature. Degenerately doped gauges (N/sub d/=10/sup 20//cm/sup 3/) exhibited a lower gauge factor (-12.7), with a more constant temperature behavior and a lower TCR (0.04%/ degrees C). The mechanisms of the piezoresistive effect and TCR in n-SiC are discussed, as well as their application towards sensors.<
>