Fabrication of FTO(P)/ZNS(P)/SI(N) Heterojunction and Study of Its Structural, Optical and Electrical Properties

Abstract

To make a heterojunction of FTO(p)/ZnS(p)/Si(n), first: FTO(p) was prepared using the thermal spraying method in order to deposit the FTO(P) layer on a glass slide, second: A semiconductor of ZnS(p) was prepared by the electrochemical deposition method in order to deposit it on the FTO(p) layer, and then the sample was treated to FTO(p)/ZnS(p) at a temperature of (150) C⁰ in a vacuum tube furnace, then it was attached to a Si(n) slide. Atomic force microscopy (AFM) showed surface images of the FTO(p)/ZnS(p) sample with dimensions of (48.5µm x 48.5µm), where the average atomic clusters appeared (89.3) nm with a semi-homogeneous granular structure, and the average surface heights of the granular cluster on the junction surface were (90.7) nm, indicating the formation of a homogeneous structure. X-ray diffraction measurements showed that the FTO(p)/ZnS(p) composite crystallized according to the hexagonal structure by electrochemical deposition method. The optical absorption spectrum of the FTO(p) substrate showed a sharp absorption peak corresponding to the wavelength of 306nm which corresponds to the energy gap (4.05) ev, and the optical absorption spectrum of the semiconductor ZnS(p) showed several optical absorption peaks corresponding to the wavelengths, indicating the presence of multiple impurity levels within the energy gap formed because of doping. The optical absorption spectrum of the FTO(P)/ZnS(p) sample was measured, where the optical absorption spectrum shows the presence of several optical absorption peaks within the visible and infrared range corresponding to several wavelengths, because of the overlap of energy levels during the deposition process in addition to the repositioning of the impurity levels within the forbidden band width of the semiconductor ZnS(p). The type of semiconductor FTO(p)/ZnS(p) was confirmed experimentally by studying the changes in the reciprocal square of the electrical capacitance in function of the applied potential. The I-V characteristic of the FTO(p)/ZnS(p)/Si(n) heterojunction showed a decrease in the threshold potential value when the junction surface is illuminated, with a constant saturation current in the reverse bias condition, which is identical to the diode condition. The ideality factor of the junction was calculated, and its value was very high (n=163), indicating the dominance of tunneling electronic transitions.