Influence of Bi on embedded nanocrystal formation and thermoelectric properties of GaAs

We have examined the influence of Bi on embedded nanocomposite formation and the resulting thermoelectric properties of GaAs. Bi implantation amorphizes the GaAs matrix, reducing both the free carrier concentration (n) and the electrical conductivity (σ). Following rapid thermal annealing, the matrix is transformed to single crystal GaAs with embedded Bi nanocrystals (NCs). In comparison to a GaAs reference, the Bi NC-containing films exhibit a sizeable reduction in thermal conductivity (κ), leading to a 30% increase in the thermoelectric figure-of-merit. We also present a universal trend for the influence of microstructure on the n-dependence of σ and κ.