Effect of Cd-doping level on the electrical, structural and photoconductivity properties of GaSe thin films

GaSe thin films were deposited by thermal evaporation technique with and without Cd doping. X-ray diffraction analysis showed that the crystallinity of doped and undoped films increases in (1014) preferred orientation direction upon annealing. Addition of cadmium dopant with excess selenium in the GaSe structure gives rise to the possibility for the existence of a CdSe phase in the highly Cd-doped samples. The room temperature conductivity and mobility values of the samples were found to be lying in between 1.3 × 101-3.4 × 102 (Ω cm)− 1, (1.2-1.5) × 10− 6 (Ω cm)− 1 and 5.9-20.9 (cm2/V s) for doped and undoped films, respectively. Dominant conduction mechanisms in doped films were determined to be thermionic emission in the high temperature region (250-400 K), tunneling in the range 160-250 K and variable range hopping mechanism between 100 and 150 K. For undoped films, thermionic emission was the dominant conduction mechanism above 250 K. Photocurrent-illumination intensity dependences indicated that the power exponent of the illumination intensity with values n > 1 implied that two recombination centers exist in the studied samples.