Electrical and Thermal Properties of B12P2 Wafers

Electrical and thermal properties of semiconducting B12P2 wafers designed as B12(Si2)x(P2)1x were measured up to high temperature. The wafers were grown at 1100?C by thermal decomposition of a B2H6-PH3-H2 gas mixture at 1100?C on Si(100) and Si(111) substrates in long-term experiments. The electrical conductivity obeyed band conduction. Thermoelectric power showed high values of 800-1000 muV/K at 400 -800 K. Measurement of the specific heat capacity by differential scanning calorimetry (DSC) yielded Debye temperatures of 1200-1300 K and Gr?neisen parameters of 0.8-0.9. Thermal diffusivity was measured with the use of ring-flash light in the laser flash method. The weak temperature dependence of thermal conductivity reflects phonon scattering by Si impurities rather than by grain boundaries. Low electrical conductivity produces lower thermoelectric figures-of-merit than BP wafers despite the high thermoelectric power.