Thermoelectric Properties of Single-Crystalline SiC and Dense Sintered SiC for Self-Cooling Devices

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We investigated the thermoelectric properties of 4H-SiC substrates and dense sintered SiC, which are expected to be candidate materials for use in self-cooling devices because of their high Seebeck coefficient, low electrical resistivity, and high thermal conductivity. The carrier concentration of 4H-SiC samples doped with nitrogen is in the range of $10^{16}$ to $10^{19}$ cm-3. The sintered SiC samples of the $\alpha$-type and $\beta$-type contain less than 1000 ppm of cation impurities and have a relative density higher than 98% with respect to single-crystalline SiC. 4H-SiC with a carrier concentration of $10^{19}$ cm-3 has the highest power factor of $2.7 \times 10^{-3}$ W$\cdot$K-2$\cdot$m-1 and a high thermal conductivity of 260 W$\cdot$K-1$\cdot$m-1 at room temperature. One-dimensional calculations for heat distribution indicate that a Si chip in a self-cooling device, which consists of 4H-SiC with a carrier concentration of $10^{19}$ cm-3, could be refrigerated more strongly than one on a copper plate under specific operating conditions.
2011-03-25