Magnetoresistance measurements in n-type CdS single crystals annealed in molten Cd and In

Abstract

Transverse magnetoresistance measurements have been made at low magnetic fields in the temperature range 77-300K in a series of n-type CdS single crystals annealed in molten Cd and In. The magnetoresistance in the Cd-annealed samples is found to be positive, obeying square law dependence on the magnetic field ( Delta rho / rho 0 varies as H2), but the magnetoresistance in samples annealed for a long time (>96 h) is much less than expected for free electron conduction. The magnetoresistance in the In-annealed samples is negative for short annealing times obeying the relation - Delta rho / rho 0 varies as Hs with s between 1 and 1.5 and decreasing with temperature. As the annealing time is increased the magnitude of negative magnetoresistance decreases and becomes positive for annealing times in the range of about 50 to 75 h. However, for annealing times exceeding about 75 h, the magnetoresistance again becomes negative. The results have been discussed on the basis of a significant contribution of the impurity band conduction to the transport phenomenon in the In-doped samples in which the concentration of ionised impurities and the compensation ratio are high due to the presence of complex acceptor systems.