Improvement of the thermoelectric performance of boron-doped silicon by blocking minority carrier diffusion on the p+/p interface

Abstract

Abstract A two-layer bulk Si material with different boron concentrations was prepared using spark plasma sintering to improve its thermoelectric performance by blocking minority carrier diffusion across its interfaces. The sintered two-layer sample (p+/p-Si) was cut to include the interface. Two monolayer samples (p+-Si, p-Si) were prepared for comparison. Seebeck coefficient mapping of the p+/p-Si surface by thermal probing confirmed a Seebeck coefficient gap between the two p-type Si layers, indicating that a band offset exists at the interface. When compared with the average resistivities and voltages for p+-Si and p-Si, the electrical resistivity in the p+/p-Si sample is almost identical, but the thermoelectric voltage is higher when the p+-part is heated more than the p-part. This indicates that bipolar carrier transport inhibition in the band offset improved the thermoelectric voltage. This bandgap engineering process and principle can be extended to other thermoelectric materials that can be processed via powder sintering.