The Electrical Properties of Black Phosphorus

The electrical conductivity of black phosphorus has been measured as a function of temperature and pressure up to 350\ifmmode^\circ\else\textdegree\fi{}C and 8000 kg/${\mathrm{cm}}^{2}$. The Hall constant of the same material has been measured as a function of temperature at atmospheric pressure. At low temperatures $p$-type impurity conduction is observed; at high temperatures the phosphorus is an intrinsic semiconductor with a gap width of 0.33 ev. The mobilities at 27\ifmmode^\circ\else\textdegree\fi{}C are 350 ${\mathrm{cm}}^{2}$/volt sec and 220 ${\mathrm{cm}}^{2}$/volt sec for the holes and electrons, respectively. Application of hydrostatic pressure decreases the gap at a rate $\frac{\mathrm{VdW}}{\mathrm{dV}}=8.3$ ev. The results are also interpreted in terms of a two-dimensional semiconductor model.