The investigation of effect of Se concentration on the structural, electrical and optical properties of in: CdSe thin films produced by electrochemical deposition method

In:CdSe precursor films were produced using electro-deposition method. In:CdSe precursor films were grown chemically onto ITO-coated glass substrates. They were electro-deposited on indium tin oxide (ITO) coated substrates under -0,95 V constant potential using Ag/AgCI reference electrode. Deposition solutions were prepared using 10mM CdCI2, 10 mM InCI3, 200 mM LiCI, and H2SeO3 source with a concentration changing from 5 mM to 35 mM by a step of 5 mM. HCI was used to adjust the pH values of the solutions. Structural and morphological studies of each produced film are analyzed in detail. Produced In:CdSe thin films are characterized by SEM-EDX, XRD, UV-VIS and Hall-Effect measurements. SEM studies shows that surface formations of In:CdSe precursor films vary depending on the Se concentration. XRD analyses show that In:CdSe thin films have CdIn2Se4 phase which has a tetragonal cyrstal structure. Forbidden energy band gaps of semiconductor thin films are calculated using UV-VIS absorbance spectra and Tauc equation. Forbidden energy band gaps of the films vary between 1,98 eV and 2,23 eV. Hall-Effect measurements show that all coatings are of n-type semiconductor. Donor concentration varies between -1,3x1017 and -4,09x1018 1/cm3. It is observed that conductivity of In:CdSe films decreases from 73,2 (Ωcm)-1 to 24,2 (Ωcm)-1 due to the increase in Se concentration in the solution. It is seen that mobility of the films is proportional to the increase in Se atomic percentage. The increase in mobility is caused most likely by the decrease in donor concentration depending on the Se percentage.