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<p>A high-performance ultraviolet (UV) photodetector based on an n–TiO<sub>2</sub>/p–Si heterojunction was fabricated using a cost-effective sol–gel spin-coating technique. The structural, morphological and optical properties of the anatase-phase TiO<sub>2</sub> thin films were systematically characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), Raman spectroscopy and photoluminescence measurements. The fabricated heterojunction exhibited pronounced diode-like rectifying behavior under dark conditions, confirming the formation of a well-defined n–TiO<sub>2</sub>/p–Si junction. Under UV–A illumination (365&#xa0;nm), the device demonstrated a strong photocurrent response, while exhibiting only a negligible change in current under ambient visible illumination, indicating effective UV selectivity. Key photodetection parameters, including responsivity, detectivity and effective photoconductive gain were evaluated as a function of the applied reverse bias. The responsivity and detectivity increased monotonically with bias due to enhanced carrier collection efficiency, whereas the photo-to-dark current ratio (PDCR) decreased at higher bias voltages as a result of bias-induced dark current enhancement associated with depletion-width expansion and field-assisted leakage mechanisms. Maximum values of responsivity (~ 47&#xa0;A W⁻<sup>1</sup>) and detectivity (~ 1.1 × 10<sup>14</sup> Jones) were achieved under reverse bias. The transient photoresponse exhibited rise and fall times of approximately 660 ms and 800 ms respectively. The photodetection mechanism is attributed to the combined effects of surface oxygen adsorption–desorption dynamics in the TiO<sub>2</sub> layer and the favorable band alignment at the n–TiO<sub>2</sub>/p–Si interface, which forms a hole-blocking junction that facilitates efficient charge separation and electron transport. The reported gain values were estimated under the assumption of unity quantum efficiency and should therefore be regarded as effective photoconductive gain. Overall, the results demonstrate that sol–gel-derived n–TiO<sub>2</sub>/p–Si heterojunctions offer a promising, low-cost platform for UV photodetection applications, with future work directed toward wavelength-dependent photoresponse and quantum efficiency measurements.</p>

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Fabrication and UV photoresponse characteristics of sol–gel spin-coated n–TiO2/p–Si heterojunction photodetector: the effect of bias voltage

  • 期刊论文

  • 发表日期：

    2026年3月9日

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  • Naif H. Al-Hardan,
  • Alaa Omar Balkhtb,
  • Mohd Narizee Mohd Nasir,
  • Lim Kar Keng,
  • Nawal Alghamdi,
  • Muhammad Azmi Abdul Hamid

摘要

A high-performance ultraviolet (UV) photodetector based on an n–TiO2/p–Si heterojunction was fabricated using a cost-effective sol–gel spin-coating technique. The structural, morphological and optical properties of the anatase-phase TiO2 thin films were systematically characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), Raman spectroscopy and photoluminescence measurements. The fabricated heterojunction exhibited pronounced diode-like rectifying behavior under dark conditions, confirming the formation of a well-defined n–TiO2/p–Si junction. Under UV–A illumination (365 nm), the device demonstrated a strong photocurrent response, while exhibiting only a negligible change in current under ambient visible illumination, indicating effective UV selectivity. Key photodetection parameters, including responsivity, detectivity and effective photoconductive gain were evaluated as a function of the applied reverse bias. The responsivity and detectivity increased monotonically with bias due to enhanced carrier collection efficiency, whereas the photo-to-dark current ratio (PDCR) decreased at higher bias voltages as a result of bias-induced dark current enhancement associated with depletion-width expansion and field-assisted leakage mechanisms. Maximum values of responsivity (~ 47 A W⁻1) and detectivity (~ 1.1 × 1014 Jones) were achieved under reverse bias. The transient photoresponse exhibited rise and fall times of approximately 660 ms and 800 ms respectively. The photodetection mechanism is attributed to the combined effects of surface oxygen adsorption–desorption dynamics in the TiO2 layer and the favorable band alignment at the n–TiO2/p–Si interface, which forms a hole-blocking junction that facilitates efficient charge separation and electron transport. The reported gain values were estimated under the assumption of unity quantum efficiency and should therefore be regarded as effective photoconductive gain. Overall, the results demonstrate that sol–gel-derived n–TiO2/p–Si heterojunctions offer a promising, low-cost platform for UV photodetection applications, with future work directed toward wavelength-dependent photoresponse and quantum efficiency measurements.