I-V characteristics of mercuric iodide crystal with different contacts

I-V characteristics of HgI₂ crystal wafers with different contacting layers, such as sputtering Au, chloroauric acid decomposed Au, colloidal graphite, were studied using Aligent4155 CVIV instrument, and analyzed according to thermoionic emission model. The results indicate that the fitting data, b, according to I = aV^b and representing ohmic contacts are 1.0291 and 0.9380, and the contact resistances are 3.0 × 10⁸Ω and 1.0 × 10⁸Ω for AuCl₃ (Au)/HgI₂ and C (graphite) /HgI₂, respectively, while 0.8341 and 3.5 × 10⁹Ω for sputtered Au. Heavily doped layer might be formed at HgI₂ surface during decomposed process of AuCl₂ which produced obvious tunnel current and idea ohmic contacts. Colloidal graphite had better chemical stability and craft of electrode fabrication did not deteriorate surface quality of HgI₂ crystal wafers. Thus, C/HgI₂ had lower contact resistance and better ohmic porperties. The higher temperature during sputtering of Au contacts leading to HgI₂ volatilization deteriorated the interface quality of HgI₂ crystal wafers, which formed no ohmic contacts.