MOCVD of Bi₂Te₃ and Sb₂Te₃ on GaAs Substrates for Thin-Film Thermoelectric Applications

Metal organic chemical vapour deposition (MOCVD) has been investigated for growth of Bi₂Te₃ and Sb₂Te₃ films on (001) GaAs substrates using trimethylbismuth, triethylantimony and diisopropyltelluride as metal organic sources. The surface morphologies of Bi₂Te₃ and Sb₂Te₃ films were strongly dependent on the deposition temperatures as it varies from a step-flow growth mode to island coalescence structures depending on deposition temperature. In-plane carrier concentration and electrical Hall mobility were highly dependent on precursor ratio of VI/V and deposition temperature. By optimizing growth parameters, we could clearly observe an electrically intrinsic region of the carrier concentration over the 240 K in Bi₂Te₃ films. The high Seebeck coefficient (of −160 μVK⁻¹ for Bi₂Te₃ and + 110 μVK⁻¹ for Sb₂Te₃ films, respectively) and good surface morphologies of these materials are promising for the fabrication of a few nm thick periodic Bi₂Te₃/Sb₂Te₃ super lattice structures for thin film thermoelectric device applications.