Electrical and Thermal Properties ofBi2Te3

Samples of both $n$-type and $p$-type ${\mathrm{Bi}}_{2}$${\mathrm{Te}}_{3}$ containing from 3\ifmmode\times\else\texttimes\fi{}${10}^{17}$ to 5\ifmmode\times\else\texttimes\fi{}${10}^{19}$ extrinsic carriers were prepared and the phase diagram in the region about ${\mathrm{Bi}}_{2}$${\mathrm{Te}}_{3}$ has been clarified. The Hall mobility parallel to the cleavage planes varies as ${T}^{\ensuremath{-}1.5}$ for holes and ${T}^{\ensuremath{-}2.7}$ for electrons. Room temperature values are ${\ensuremath{\mu}}_{p}=420$ ${\mathrm{cm}}^{2}$ ${\mathrm{v}}^{\ensuremath{-}1}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ and ${\ensuremath{\mu}}_{n}=270$ ${\mathrm{cm}}^{2}$ ${\mathrm{v}}^{\ensuremath{-}1}$ ${\mathrm{sec}}^{\ensuremath{-}1}$. The energy gap is ${E}_{g}=0.20$ electron volts. From thermal conductivity measurements over the temperature range from 77\ifmmode^\circ\else\textdegree\fi{}K to 380\ifmmode^\circ\else\textdegree\fi{}K the lattice conductivity was found to be ${\ensuremath{\kappa}}_{L}=5.10\ifmmode\times\else\texttimes\fi{}\frac{{10}^{\ensuremath{-}2}}{T}$ watt-${\mathrm{deg}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{\ensuremath{-}1}$. The sharp rise in the thermal conductivity in the vicinity of room temperature was attributed to transport of energy by ambipolar diffusion of electrons and holes.