Photoconductivity, low-temperature conductivity, and magnetoresistance studies on the layered semiconductor GaTe

Abstract

Single crystals of p-GaTe were grown by the Bridgman technique and characterized through x-ray diffraction, energy-dispersive x-ray analysis, x-ray photoemission spectroscopy, and transmission electron microscopy studies. The photoconductivity spectral response for in-plane conduction showed a peak at 747 nm (1.66 eV). Photoconductivity gain was determined in two orthogonal directions from which the majority carrier (hole) lifetimes were found to be 3.43× 10^-7 and 2.03× 10^-6s, respectively, parallel and perpendicular to the layer planes. Studies of the temperature dependence of conductivity in the directions along and perpendicular to the layer planes were carried out between 10 and 80 K. Along the layer planes the conductance G varied as lnT between 12 and 20 K, characteristic of weak localization, while between 20 and 50 K the conductivity σ varied as T^1/2. In the perpendicular direction the conductance G varied as exp(T/T₀)^1/3 between 9 and 20 K and the conductivity σ varied as exp(T/T₀)^1/4 between 20 and 50 K, characteristic of hopping conduction in two and three dimensions, respectively. Negative transverse magnetoresistance was observed at 10 K for conduction in both directions for magnetic fields H<0.4T, the increase in conductance being found to be proportional to H². Band conduction with positive magnetoresistance was observed for both current directions at T>70K. The I-V characteristics at 10 K showed quantized behavior due to electron tunneling across potential barriers caused by stacking faults between layer planes.