Nanocomposites for thermoelectric power generation: rare-earth metal monoantimonide nanostructures embedded in InGaSb and InSbAs ternary alloys

Abstract

Thermoelectric figure of merit (ZT) depends on three material properties; electrical conductivity, thermal conductivity, and Seebeck coefficient. Maximizing ZT simply requires that electrical conductivity and Seebeck coefficient be high to reduce Joule heating and to increase energy conversion efficiency while thermal conductivity needs to be low to maintain temperature gradient across a thermoelectric material. Unfortunately these three material properties are closely correlated each other in homogeneous bulk semiconductors. Recent demonstrations that employ various semiconductor materials tuned at the nanometer-scale (nanomaterials) have shown great promise in advancing thermoelectrics. Among a wide range of nanomaterials, we focus on "nanocomposites" in which semimetallic nanostructures are epitaxially embedded in a ternary compound semiconductor matrix to attempt tuning the three material properties independently. We demonstrated co-deposition of erbium monoantimonide (ErSb) and In_1-xGa_xSb or InSb_1-yAsy ternary alloy to form nanometer-scale semimetallic ErSb structures within these ternary alloys "nanocomposite" using low-pressure metal organic chemical vapor deposition. The grown nanocomposites were structurally and thermoelectrically analyzed to assess their potential for advanced thermoelectric power generation.