HALL EFFECT MEASUREMENTS OF GROUP II-VI SEMICONDUCTORS

Abstract

In the present work, “Ecopia 5000 Hall effect measurements system”, has been made operational successfully for the first time at Thermal Transport Laboratory, SCME, NUST, Islamabad. Electrical characterization of ZnO and CdS thin films has been done with the help of Ecopia 5000 Hall Effect measurement system. ZnO and CdS thin films have been prepared by sol gel and close space sublimation techniques. These films were characterized by SEM, XRD, EDS and Hall Effect measurement for their morphological, structural, and electrical properties respectively. The electrical resistivity‟s of ZnO and CdS thin films were found to be of order of 103 and 105 ohm-cm respectively. Decreasing trend for magneto resistance as a function of temperature was also observed for both ZnO and CdS films. The change in the resistivity of these materials was about 2% of the order in the change of resistivity when these films were subjected to magnetic field of 0.55 T which confirmed anisotropic magneto resistance phenomenon in both of these semiconductor films. Resistivity and sheet resistance variations with thickness were also determined for these films. In ZnO and CdS thin films, as thickness and temperature increased the resistivity of both of these films decreased which confirmed semiconductor like behavior. I-V characterizations for these films under light and dark conditions showed features which is responsible for its applications as photovoltaic materials. The resistivity of ZnO and CdS thin films has followed the hopping model which also confirmed the semiconductor like nature of these thin films. As for ZnO and CdS films, hopping distance decreased while hopping energy increased linearly with rising temperature. Both these films have followed necessary conditions for Mott‟s VRH mechanism. The said model is applied to dc electrical resistivity data.