Fabrication and characterization of CdS/CIS nanowire heterojunctions

Nanowire arrays of CIS were formed inside porous alumina templates by pulsed potential electrodeposition. Close to stoichiometric CIS phase in a chalcopyrite crystal structure with a = 5.782 Å and c = 11.619 Å. was obtained. Atomic weight fractions of Cu, In and Se were 20%:38%:42%. Arrays of cadmium sulfide nanowire were also fabricated inside the porous AAO templates. The XRD pattern of the CdS nanowires indicated the hexagonal lattice with the dominant crystal planes of <100>, <002> and <101>. The absorption spectrum of as-prepared CdS nanowires showed the blue shift of the absorption edge from the bulk crystal value of 515 nm to 490 nm. Al/CIS and Au/CdS Nanowire Schottky diodes were fabricated and their electrical properties were investigated. Diode analysis on the Au/CdS device reveled that the values of the effective diode ideality factor (A) and the effective reverse saturation current (J0,), were, 8.0 and 0.32 mA/cm² in the dark, and 9.9 and 0.9 mA/cm² under illumination. The fact that the measured values of effective diode ideality factor (A) were larger than 2.0 indicates that the dominant mechanism of electron transport across the junction is likely to be tunneling and/or interface state recombination, or a combination of these two.