Applied Surface Science, Vol.252, No.15, 5508-5511, 2006
Van der Pauw resistivity measurements on evaporated thin films of cadmium arsenide, Cd3As2
Cadmium arsenide is a II-V semiconductor, exhibiting n-type intrinsic conductivity with high mobility and narrow bandgap. It is deposited by thermal evaporation, and has shown the Schottky and Poole-Frenkel effects at high electric fields, but requires further electrical characterisation. This has now been extended to low-field van der Pauw lateral resistivity measurements on films of thickness up to 1.5 mu m. Resistivity was observed to decrease with increasing film thickness up to 0.5 mu m from about 3 x 10(-3) Omega M to 10(-5) Omega m, where the crystalline granular size increases with film thickness. This decrease in resistivity was attributed to a decrease in grain boundary scattering and increased mobility. Substrate temperature during deposition also influenced the resistivity, which decreased from around 10(-4) Omega M to (10(-5) to 10(-6)) Omega M for an increase in substrate deposition temperature from 300 K to 423 K. This behaviour appears to result from varying grain sizes and ratios of crystalline to amorphous material. Resistivity decreased with deposition rate, reaching a minimum value at about 1.5 nm s(-1), before slowly increasing again at higher rates. It was concluded that this resulted from a dependence of the film stoichiometry on deposition rate. The dependence of resistivity on temperature indicates that intercrystalline barriers dominate the conductivity at higher temperatures, with a hopping conduction process at low temperatures. (c) 2006 Elsevier B.V All rights reserved.