Lung-Chien Chen

Bio: Lung-Chien Chen is an academic researcher. The author has contributed to research in topics: Responsivity & Ultraviolet. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

Si-Based ZnO Ultraviolet Photodiodes

Abstract: Semiconductor-based ultraviolet (UV) photodiodes have been continuously developed that can be widely used in various commercial, civilian areas, and military applications, such as optical communications, missile launching detection, flame detection, UV radiation calibra‐ tion and monitoring, chemical and biological analysis, optical communications, and astro‐ nomical studies, etc. [1-2]. All these applications require very sensitive devices with high responsivity, fast response time, and good signal-to-noise ratio is common desirable charac‐ teristics. Currently, light detection in the UV spectral range still uses Si-based optical photo‐ diodes. Due to the Si-based photodiodes are sensitive to visible and infrared radiation, the responsivity in the UV region is still low [3-5]. To avoid these disadvantages, wide-bandgap materials (such as diamond, SiC, III-nitrides and wide-bandgap II–VI materials) are under intensive studies to improve the responsivity and stability of UV photodiodes, because of their intrinsic visible-blindness [6].

Oxide bipolar electronics: materials, devices and circuits

Abstract: We present the history of, and the latest progress in, the field of bipolar oxide thin film devices. As such we consider primarily pn-junctions in which at least one of the materials is a metal oxide semiconductor. A wide range of n-type and p-type oxides has been explored for the formation of such bipolar diodes. Since most oxide semiconductors are unipolar, challenges and opportunities exist with regard to the formation of heterojunction diodes and band lineups. Recently, various approaches have led to devices with high rectification, namely p-type ZnCo2O4 and NiO on n-type ZnO and amorphous zinc-tin-oxide. Subsequent bipolar devices and applications such as photodetectors, solar cells, junction field-effect transistors and integrated circuits like inverters and ring oscillators are discussed. The tremendous progress shows that bipolar oxide electronics has evolved from the exploration of various materials and heterostructures to the demonstration of functioning integrated circuits. Therefore a viable, facile and high performance technology is ready for further exploitation and performance optimization.

Role of p-NiO electron blocking layers in fabrication of (P-N):ZnO/Al:ZnO UV photodiodes

Abstract: We report the fabrication and characterization of ZnO-based UV photodiodes with p-NiO as an intermediate electron blocking layer (EBL). The n-ZnO and p-ZnO layers are deposited by automated spray pyrolysis technique and NiO layers by r.f.magnetron sputtering. For the realization of p-ZnO, dual acceptor method has been adopted by doping equimolar concentration of group-V elements P and N (0.75 at%) simultaneously in ZnO. The formation of p-type characteristics in ZnO is confirmed by Hall measurement and X-ray photoelectron spectroscopy (XPS) analysis. The n-ZnO is doped with Al (3 at%) in order to improve the electrical properties. The properties of sputtered NiO layers have been investigated under three different deposition temperatures of 300 °C, 350 °C and 400 °C. By analyzing structural and electrical properties, it is revealed that NiO deposited at 350 °C possess better crystallinity and electrical properties. The optimum p-ZnO and n-ZnO layers are stacked upon ITO substrates to form ZnO-based p-n junctions. The effect of addition of NiO as an electron blocking layer (EBL) between the p-n junctions is investigated by analyzing the current density-voltage (J-V) and UV photoresponse properties. The fabricated ZnO-based UV photodiodes with NiO EBL exhibits a high photoresponsivity (R) value of 5.53 A/W with external quantum efficiency (EQE) value of 1.87 × 103%.

Photodetection Properties of ZnO/Si Heterojunction Diode: A Simulation Study

Abstract: This article reports simulation study and performance analysis of ZnO/Si heterojunction-based UV–visible photodetector. Different electrical and optical parameters such as energy band diagram, electric field profile, dark current, quantum efficiency, responsivity, detectivity, and noise equivalent power of ZnO/Si heterojunction-based photodetector have been simulated as a function of device thickness, operating wavelength, and applied reverse bias voltage. The simulation software ATLAS™ in SILVACO package is used to describe the effect of ZnO/Si interface properties on its photodetection. The value obtained for external quantum efficiency, responsivity, and specific detectivity for ZnO/Si heterojunction-based photodetector were ∼93%, 0.36 A/W, and 7.2 × 1010 cm Hz½ W−1, respectively. The estimated values for dark current and noise equivalent power were of the order of 10−14 A and 10−11 W, respectively.

Interfacial modification in Si/CdO heterojunction by Ge doping for optoelectronic applications

Abstract: The electrical properties of Ge-doped CdO (CdO:Ge) films grown on p-Si were studied in this work. The focussing was on the effect of optoelectrical properties of CdO:Ge film on the optoelectrical properties of the constructed p–n heterojunction, as well as to study the dependence of the optosensitivity and optoresponse of the heterojunction on the Ge% doping level. The characterisation of the transparent conducting oxide CdO:Ge layer was performed by the X-ray diffraction, SEM, electrical measurements, and spectral photometry. A strong optosensitivity was found especially for the p–n heterojunction that used 0.16 wt% Ge-doped CdO, attaining a great value of about 60,000% comparing to undoped CdO. In addition, a good value of optical response of 319.4 mA/W for the p–n heterojunction constructed with 0.25 wt% Ge-doped CdO. The results show that CdO:Ge/p-Si heterojunctions act as very good candidates for constructing high-efficiency photodetectors.

High-speed photoresponse properties of ultraviolet (UV) photodiodes using vertically aligned Al:ZnO nanowires

Abstract: Ultraviolet (UV) photodiodes with fast photoresponse properties were fabricated using vertically aligned aluminum doped ZnO nanowires. Stable p-type ZnO have been achieved by doping equimolar concentration of P-N (0.75 at.%) simultaneously in ZnO. The vertically aligned and electrically conducting n-type Al (3 at.%) doped ZnO nanowires were grown by a simple aqueous chemical growth process. The structural, morphological, optical, and electrical properties were investigated. For the fabrication of UV photodiodes, the optimum p-type ZnO layers and n-type ZnO nanowires were stacked upon ITO substrate. A 250 nm thin NiO was deposited as an electron blocking layer (EBL) in between the ZnO p–n junctions. The current density–voltage (J–V) characteristic of the fabricated UV photodiode was measured under dark and UV illumination conditions. Under a reverse bias of 3 V, the device exhibits a high photoresponsivity (R) value of 15.07 (A/W) upon illumination of UV light (λ = 365 nm). The fabricated photodiode exhibits a fast photoresponse switching characteristics with a response and recovery time calculated as 61 ± 11 and 455 ± 41 ms, respectively. The role of vertically aligned nanowires in the formation of oxygen interstitial (Oi) defects and its impact on improving the UV photoresponse properties were investigated.