Fabrication and Characterization of n-In2S3/p-Si Based Heterojunction Photodetectors

In2S3 is a preferred semiconductor in optoelectronic applications due to its favorable bandgap. In this study, In2S3 films were prepared at different S/In molar ratios by chemical solution method and their structural, morphological and optical properties were examined. In addition, heterojunction photodetector devices with n- In2S3/p-Si structure were prepared by coating In2S3 thin films on p-type silicon substrates with the spin coating technique. According to X-ray diffraction (XRD) results, all films crystallize in a tetragonal structure. Scanning electron microscope (SEM) images show that the films have a granular structure. The band gaps of the films vary between 2.84 eV and 2.94 eV depending on the S/In ratio. According to the measurements made in the dark environment, the devices have a pn junction diode characteristic structure. Measurements made under visible light show that the devices respond to light. Under 5mW/cm2 visible light, the photosensitivity of the devices reaches a high value of 3396. The maximum photoresponsivity and specific detectivity were recorded as 9×10-3 A/W, and 6.2×1010 Jones. Moreover, these devices have rise and decay times of less than 1 second. By adjusting the S/In ratio, the dark current of the devices was reduced to 3.7×10-10 A. This low dark current also increased the specific detectivity values of the devices up to 6.2×1010 Jones. The results of this study clearly show that In2S3 semiconductor is a highly compatible material for forming pn junction structure with p-type silicon. In addition, while preparing the In2S3 semiconductor, the change in the S/In ratio in the solution significantly affects both the physical properties of the films and the parameters of the devices.