Antimony as an amphoteric dopant in lead telluride

We elucidate the amphoteric nature of antimony as a dopant in PbTe. Band-structure calculations show that Sb substituting for Pb is a donor and that Sb on the Te site is an acceptor giving rise to a large excess density of states (DOS). Experimentally, in Te-rich Pb_1−xSb_xTe samples, ¹²⁵Te NMR spectroscopy shows that Sb substitutes for Pb and transport data reveal that it then acts as a simple donor. In Pb-rich PbSb_xTe_1−x samples, ¹²⁵Te NMR shows that little Sb substitutes for Te when samples are prepared above 770 K and then quenched; ²⁰⁷Pb NMR shows four types of charge carriers, but only a majority hole and a minority electron contribute to transport. Sb acts as an acceptor in PbSb_xTe_1−x, but the large DOS calculated must correspond to a large concentration of localized holes and the Seebeck coefficient is not enhanced.