Enhancement of the electrical performance of TiO 2 /p-Si heterojunction diode by Gadolinium doping
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Enhancement of the electrical performance of TiO2/p‑Si heterojunction diode by Gadolinium doping Serif Ruzgar1 Received: 1 July 2020 / Accepted: 29 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this study, the T iO2/p-Si and Gd:TiO2/p-Si heterojunctions were fabricated by sol–gel method. The UV–Vis spectroscopy was performed to evaluate optical characteristics of TiO2 and Gd:TiO2 thin films. It was observed that the optical band gap, transmittance, extinction coefficient and optical dielectric constants of TiO2 thin film were increased with Gd content. The electrical features of the heterojunction diodes were analyzed and compared by conventional I–V measurements under dark condition. With the Gd doping, the ideality factor of T iO2/p-Si diode decreased from 8.97 to 3.87 and rectification ratio increased from 1.59 × 103 to 1.45 × 106. The serial resistance of diodes was calculated by both Norde and Cheung methods. The high series resistance value and high dark current of the T iO2/p-Si diode have been successfully surmounted with the Gd doping. Moreover, the photovoltaic properties of the Gd:TiO2/p-Si photodiode were studied under various illumination intensities. It has been shown that the Gd:TiO2/p-Si diode can be utilized as a photosensor due to its reaction to light. Keywords Thin films · Gd-doped T iO2 · Diode parameters · Photodetector · Sol–gel
1 Introduction In recent years, doped metal oxides have attracted great attention due to their unusual electrical optical and structural properties as well as their superior performance in device applications than parent materials. Among parent metal oxides, n-type TiO2 semiconductor is widely investigated due to excellent properties such as low toxicity, high oxidizing capacity, wide optical band gaps (band gap > 3 eV), chemical and structural stability, resistance to photodegeneration and long lifetime of photogenerated charges [1–4]. Also, its low cost, good thin film formation and the superior optoelectrical properties mentioned above make TiO2 a useful material for a variety of applications such as photovoltaic, photocatalysts, chemo-sensors, dye-sensitized solar cells, gas sensing, UV detector and heterojunction diodes [5–8]. Among these devices, heterojunction diodes are of great importance in semiconductor research communities due to their application areas such as solar cells and photodiodes [9–11]. Improving the performance of heterojunction * Serif Ruzgar [email protected] 1
Department of Opticianry Program, Vocational School of Health Services, Batman University, Batman, Turkey
structures is important to achieve higher efficiency from their device applications. In this context, the control of the electrical behavior of heterojunction devices is crucial and strongly dependent on the homogeneity of the interfaces of the structure [12, 13]. These controllable parameters can be listed as barrier height, series resistance, turn-on voltage, ideality factor and interface states. Despite all its
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