Optical and electrical properties of GaSe thin films

GaSe thin films were deposited at room temperature onto glass substrate and carbon stub by thermal evaporation technique. The X-ray diffraction analysis showed that both as-deposited films and those vacuum annealed at 475 K for 1 h are amorphous in nature. The elemental analysis of thin films deposited onto carbon stub revealed that nearly stoichiometric films of Ga0.98Se1.02 could be deposited with a deposition rate of 1.8 nm/s. The optical transmittance and reflectance spectra of as-deposited films were recorded at normal light incident in the wavelength spectral range 600-3000 nm. The refractive index in the transmission and low absorption region is adequately described by Sellmeier dispersion relation. The mechanism of the optical absorption follows the rule of indirect optical transition and the corresponding energy was estimated. The I-V characteristics of MSM configuration system have indicated an ohmic behaviour with similar In electrodes. However, for Al/GaSe/In system non-ohmic behaviour was observed. The data of the forward branch were analyzed. The dc measurements were made on the as-deposited GaSe films in the temperature range 130-475 K. The obtained result revealed two distinct regions. The mechanisms of such region were analyzed.