Electrical Properties of Black Phosphorus Single Crystals

Large single crystals of black phosphorus have been grown under high pressure, and by using the crystals, the Hall measurements have been done in a range from 4.2 K to 550 K. All the undoped samples have exhibited p -type conduction, while we have succeeded in obtaining n -type crystals by doping Te impurity. The effective acceptor concentrations N A -N D of the p -type samples and those of donor in n -type samples N D -N A have been in the range of 2∼5×10 15 cm -3 and 2∼3×10 16 cm -3 , respectively. From the intrinsic range of the conductivity, the energy gap has been estimated to be 0.335 eV, The acceptor and donor activation energies have been determined to be ∼18 meV and ∼39 meV, respectively. The Hall mobility of the hole reaches its maximum of 6.5×10 4 cm 2 /V·sec around 20 K. The anisotropies of the conductivity and the mobility along the three crystal axes have been investigated.