Thermoelectric Properties of Superlattice Materials with Variably Spaced Layers

D.G. Walker Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee 37212, USA Abstract Variably spaced semiconductor superlattice (VSSL) have exhibited superior electron mobility and rectification because of electronic level alignment. We have investigated the thermoelectric properties of VSSL structures using a self-consistent non-equilibrium Green’s function (NEGF) quantum model to capture the ballistic electron transport and an atomistic NEGF model to capture the phonon transport. A figure of merit was calculated as a function of temperature for two VSSL strain silicongermanium materials and a non-VSSL material. Calculation of ZT versus temperature for a VSSL demonstrated a 17 times increase in power factor at the expense of a 4 times increase in thermal conductivity at room temperature compared to a comparable uniform SL. Calculation determined a ZT = 0.20 for a VSSL compared to ZT = 0.04 for non-VSSL material at 400K. VSSL’s prove to be a candidate material to further increased ZT near room temperature for superlattice materials.