Influence of hydrostatic pressure on the electrical conductivity of tellurium single crystals

The influence of hydrostatic pressure up to 5000 kp/cm2 on the electrical conductivity of differently doped tellurium single crystals is investigated in the temperature range from 165 to 430 °K. For extrinsic and intrinsic tellurium the conductivity increases exponentially with pressure. The pressure coefficient π = d (In σ)/dp is independent of temperature in the extrinsic region, rises appreciably then and finally decreases proportional to 1/T in the intrinsic range. The decrease of the energy gap with pressure at a rate of dEg/dp = −1.3 × 10−5 eV cm2/kp is the major effect in the intrinsic region. Possible mechanisms for the pressure dependence in extrinsic tellurium are discussed. It is shown that a decrease of the effective mass with pressure cannot account for the experimental results and that probably an enhancement of the dielectric constant by pressure leads to the observed increase of the mobility.