Layer by layer growth of Bi/sub 2/Te/sub 3/ epitaxial thermoelectric heterostructures

Epitaxial films of n- and p-type (0001)Bi/sub 2/Te/sub 3/ with carrier concentrations between 1/spl times/10/sup 18/ and 8/spl times/10/sup 19/ cm/sup -3/ have been grown by hot wall epitaxy at the surface of mica. Granular textured films have been grown on barium fluoride substrates. A regular system of growth steps of 1 nm height was observed at the surface of the Bi/sub 2/Te/sub 3/ films grown on mica at 600 K. The spirals (m/spl ap/10/sup 6/ cm/sup -2/) were detected by AFM at the surface of the thermoelectric films when substrate temperature was increased to 640 K. Steps at the surface of freshly cleaved BaF/sub 2/ substrate promote the formation of a grains in the Bi/sub 2/Te/sub 3/ film and rough surface. The /spl alpha/ /sup 2//spl sigma/ for the Bi/sub 2/Te/sub 3/ films with electron and hole conductance at 300 K was in the range 40-60 /spl mu/W cm/sup -1/ K/sup -2/.