High-Output-Power Densities from MBE-grown n- and p-Type PbTeSe-based Thermoelectrics via Improved Contact Metallization

Abstract : Electrical power densities of up to 33 W/sq cm and up to 12 W/sq cm were obtained for n-type and p-type PbTeSe-based stand-alone thermoelectric devices, respectively, at modest temperature gradients of 200 deg C (Tcold=25 deg C). These large power densities were enabled by greatly improving electrical contact resistivities in the thermoelectric devices. Robust electrical contacts with contact resistivities as low as 3.9x10(exp 6) ohm-sq cm and 4.0x10(exp 6) ohm-sq cm for n- and p-type telluride-based-materials, respectively, were developed by investigating several metallization schemes and contact layer doping/alloy combinations, in conjunction with a novel contact application process. This process exposes heated semiconductor surfaces to an atomic hydrogen flux under high vacuum for surface cleaning (oxide and carbon removal), followed immediately by an in-situ electron-beam evaporation of the metal layers.