CHARACTERIZATION OF N-TYPE BETA-SIC AS A PIEZORESISTOR

SiC is currently being investigated for device applications involving high temperatures. In this paper, 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(16)-10(17)/cm3) 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(d) = 10(20)/cm3) 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.