Van der Pauw resistivity measurements on evaporated thin films of cadmium arsenide, Cd 3As 2
Abstract
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 μm. Resistivity was observed to decrease with increasing film thickness up to 0.5 μm from about 3 × 10 -3 Ω m to 10 -5 Ω 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 Ω m to (10 -5 to 10 -6) Ω 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.
- Publication:
-
Applied Surface Science
- Pub Date:
- May 2006
- DOI:
- 10.1016/j.apsusc.2005.12.151
- Bibcode:
- 2006ApSS..252.5508D
- Keywords:
-
- 72.20.Fr;
- 72.80.Ey;
- 81.15.Ef;
- Low-field transport and mobility;
- piezoresistance;
- III-V and II-VI semiconductors;
- Vacuum deposition