We have theoretically investigated the in-plane lattice thermal conductivity of a quantum-dot superlattice. The calculations were carried out for a structure that consists of multiple layers of Si with randomly distributed Ge quantum dots separated by wetting layers and spacers. Our model takes into account scattering of acoustic phonons on spherical quantum dots, and corresponding modification of the phonon dispersion relation. The finite acoustic mismatch between Si and Ge is also taken into account. The obtained results are important for the most recently suggested applications of SiGe quantum-dot superlattices for thermoelectric devices.

We theoretically investigated electron and phonon transport in a quantum superlattice and evaluated a possible thermoelectric figure of merit increase. The presented model takes into account electron and phonon transport modifications due to the space confinement caused by the mismatch in electronic and thermal properties between dot and host materials. The numerical calculations were carried out for a structure that consists of multiple layers of Si with regimented quantum dots separated by wetting layers and spacers. Transport coefficients (electric conductivity, Seebeck coefficient and lattice thermal conductivity) were calculated as functions of quantum dot volume fraction for different dot sizes. It is shown that additional thermoelectric figure of merit enhancement due to the presence of quantum dots may be obtained. The predicted enhancement is mostly due to the significant drop in the lattice thermal conductivity caused by the acoustic phonon scattering by quantum dots.

We present Raman scattering by optical phonons in self-assembled Ge quantum dot superlattices grown by solid-source molecular beam epitaxy. The Ge quantum dots are vertically correlated and have different average sizes and dot morphologies. The GeGe optical phonon frequency was mainly caused by strain relaxation effects. Experimentally observed GeGe optical phonon modes were compared with calculated values using the deformation potential theory, indicating that the strain relaxation of Ge quantum dot superlattices arises not only from atomic intermixing but also from the morphology transition in dot formation.

We provide an outlook of some important state variables for emerging nanoelectronic devices. State variables are physical representations of information used to perform information processing via memory and logic functionality. Advances in material science, emerging nanodevices, nanostructures, and architectures have provided hope that alternative state variables based on new mechanisms, nanomaterials, and nanodevices may indeed be plausible. We review and analyze the computational advantages that alternate state variables may possibly attain with respect to maximizing computational performance via minimum energy dissipation, maximum operating switching speed, and maximum device density.

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