Optimization of Seebeck coefficients of strain-symmetrized semiconductor heterostructures
Abstract
A nonmonotonic thermopower (S) as a function of the carrier concentration (ne) has been reported for III-V semiconductor superlattices (SLs), deviating from the Pisarenko relation. However, | S | has been shown to decrease with increasing ne in n-type Si/Ge heterostructures, the widely used systems for numerous applications. Here, we illustrate that S of a SinGem SL, with n Si and m Ge monolayers, can deviate from the Pisarenko relation depending on the period and the composition; for example, oscillations of S of a Si12Ge12 SL reach a peak | S | = 540 μ V/K at n e = 1.3 × 10 20 cm-3, 5.4 times higher than that of bulk Si at the same doping level. Additionally, S shows an interesting sign-change nature at certain carrier concentrations. We demonstrate the direct relationship between the electronic structure and S of strain-symmetrized Si/Ge SLs using two independent modeling approaches. We anticipate that this relationship will provide insight into fully exploiting S as a tool to control electronic properties of Si/Ge heterostructures as well as future technology-enabling materials. Furthermore, we expect that this analysis will encourage future investigations to enhance thermoelectric properties of a broad class of semiconductor SLs in the high-doping regime.
- Publication:
-
Applied Physics Letters
- Pub Date:
- November 2019
- DOI:
- 10.1063/1.5123294
- Bibcode:
- 2019ApPhL.115u1602P