Schottky diode properties of CuInSe2 films prepared by a two-step growth technique

CuInSe2 films were synthesized by a thermal evaporation method on both glass and Mo coated glass substrates. To obtain Al/CuInSe2/Mo Schottky diode, Al metal was evaporated on the upper surface of CuInSe2 as a front contact and electrical properties of the structure were analyzed. The structural and optical behaviors of the CuInSe2 thin films were also investigated. The X-ray diffraction studies showed that the chalcopyrite CuInSe2 was obtained with a preferential orientation in the (1 1 2) plane with lattice parameters a and c as 0.577 and 1.161 nm, respectively. Mo back contact layer had a preferential orientation in the (1 1 0) plane. Scanning electron microscopy equipped with energy dispersive spectroscopy revealed an irregular and rough surface morphology with Cu-rich protruding regions. Optical studies showed the existence of three different band gaps, which were determined as 1.06, 1.17 and 1.39 eV, respectively. From the Hall Effect measurements, we determined the carrier concentration of CuInSe2 films as 4.0 × 1017 cm−3. The electrical properties of the CuInSe2 films were further studied by fabricating Al/p-CuInSe2/Mo structures and obtaining their forward and reverse bias current–voltage characteristics in a wide temperature range of 100–300 K, in steps of 25 K. A thorough analysis of the forward bias current–voltage characteristics based on thermionic emission theory showed that the zero bias barrier height increases while series resistance and ideality factor decreases with an increase in temperature. After a barrier height inhomogeneity correction, the Richardson constant and mean barrier height were found to be 34.71 A/cm2 K2 and 0.72 eV, respectively.