Carrier pocket engineering to design superior thermoelectric materials using GaAs/AlAs superlattices

A large enhancement in the thermoelectric figure of merit for the whole superlattice, Z(3D)T, is predicted for short-period GaAs/AlAs superlattices relative to bulk GaAs. Various superlattice parameters (superlattice growth direction, superlattice period, and layer thicknesses) are explored to optimize Z(3D)T, including quantum well states formed from carrier pockets at various high symmetry points in the Brillouin zone. The highest room-temperature Z(3D)T obtained in the present calculation is 0.41 at the optimum carrier concentration for either (001)- or oriented GaAs (20 Angstrom)/AlAs (20 Angstrom) superlattices, which is about 50 times greater than the corresponding ZT for bulk GaAs. (C) 1998 American Institute of Physics. [S0003-6951(98)01546-0].