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1 – 10 of 217Chee Yong Fong, Sha Shiong Ng, NurFahana Mohd Amin, Fong Kwong Yam and Zainuriah Hassan
This study aims to explore the applicability of the sol-gel-derived GaN thin films for UV photodetection.
Abstract
Purpose
This study aims to explore the applicability of the sol-gel-derived GaN thin films for UV photodetection.
Design/methodology/approach
GaN-based ultraviolet (UV) photodetector with Pt Schottky contacts was fabricated and its applicability was investigated. The current-voltage (I-V) characteristics of the GaN-based UV photodetector under the dark current and photocurrent were measured.
Findings
The ideality factors of GaN-based UV photodetector under dark current and photocurrent were 6.93 and 5.62, respectively. While the Schottky barrier heights (SBH) for GaN-based UV photodetector under dark current and photocurrent were 0.35 eV and 0.34 eV, respectively. The contrast ratio and responsivity of this UV photodetector measured at 5 V were found to be 1.36 and 1.68 μA/W, respectively. The photoresponse as a function of time was measured by switching the UV light on and off continuously at different forward biases of 1, 3 and 6 V. The results showed that the fabricated UV photodetector has reasonable stability and repeatability.
Originality/value
This work demonstrated that GaN-based UV photodetector can be fabricated by using the GaN thin film grown by low-cost and simple sol-gel spin coating method.
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Shireen Mohammed Abed, Sabah M. Mohammad, Zainuriah Hassan, Aminu Muhammad and Suvindraj Rajamanickam
The purpose of this study is to fabricate an ultraviolet (UV) metal-semiconductor-metal (MSM) photodetector based on zinc oxide nanorods (ZnO NRs) grown on seeded silicon (Si…
Abstract
Purpose
The purpose of this study is to fabricate an ultraviolet (UV) metal-semiconductor-metal (MSM) photodetector based on zinc oxide nanorods (ZnO NRs) grown on seeded silicon (Si) substrate that was prepared by a low-cost method (drop-casting technique).
Design/methodology/approach
The drop-casting method was used for the seed layer deposition, the hydrothermal method was used for the growth of ZnO NRs and subsequent fabrication of UV MSM photodetector was done using the direct current sputtering technique. The performance of the fabricated MSM devices was investigated by current–voltage (I–V) measurements. The photodetection mechanism of the fabricated device was discussed.
Findings
Semi-vertically high-density ZnO (NRs) were effectively produced with a preferential orientation along the (002) direction, and increased crystallinity is confirmed by X-ray diffraction analysis. Photoluminescence results show a high UV region. The fabricated MSM UV photodetector showed that the ZnO (NRs) MSM device has great stability over time, high photocurrent, good sensitivity and high responsivity under 365 nm wavelength illumination and 0 V, 1 V, 2 V and 3 V applied bias. The responsivity and sensitivity for the fabricated ZnO NRs UV photodetector are 0.015 A W-1, 0.383 A W-1, 1.290 A W-1 and 1.982 A W-1 and 15,030, 42.639, 100.173 and 334.029, respectively, under UV light (365 nm) illumination at (0 V, 1 V, 2 V and 3 V).
Originality/value
This paper uses the drop-casting technique and the hydrothermal method as simple and low-cost methods to fabricate and improve the ZnO NRs photodetector.
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Guohua Jiang, Dongmei Zhao and Bo Zhao
The purpose of this paper is to investigate the optoelectronic properties of the multichannel ZnO UV photodetectors.
Abstract
Purpose
The purpose of this paper is to investigate the optoelectronic properties of the multichannel ZnO UV photodetectors.
Design/methodology/approach
ZnO nanowires were assembled by dielectrophoresis for the UV photodetectors. Different ZnO channels were adjusted by different alternating current voltages and investigated for UV optoelectronic properties.
Findings
The number of the ZnO channels increases with the enhancing alternating current voltage. Optimum performance of the UV photodetectors is obtained with more channels.
Originality/value
Dielectrophoresis is a promising method for controllable assembly of multichannel ZnO photodetectors. ZnO photodetectors with more channels demonstrate a good response to 380-nm UV light, which shows great potential application in UV photodetector.
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Ying Wei, Xueyuan Cai, Jinzhi Ran and Jianhong Yang
The purpose of this paper is to investigate the dependence of dark current on threading dislocations (TDs) in relaxed Ge layer for Ge/Si heterojunction photodetectors.
Abstract
Purpose
The purpose of this paper is to investigate the dependence of dark current on threading dislocations (TDs) in relaxed Ge layer for Ge/Si heterojunction photodetectors.
Design/methodology/approach
The analysis of the effects of TDs is based on SRH generation and recombination mechanism used in two‐dimensional drift‐diffusion numerical simulation.
Findings
It is found that the TDs in Ge layer acting as the recombination centers lead to large dark current densities of devices, and the recombination rate is affected by the impurity out‐diffusion from Si substrate. Besides, the TDs, being the acceptor‐like defects simultaneously, form band barrier at Si/Ge interface with lightly doped Si substrates, thus limiting the minority carrier transport and resulting in low dark current densities.
Originality/value
The simulation results are excellently consistent with the experimental data and indicate that the reduction of threading dislocation densities (TDDs), especially in Ge buffer layer, dramatically decreases dark currents densities of Ge/Si photodetectors. The investigation can be applied to imbue devices with desired characteristics.
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A.F. Abd Rahim, M.R. Hashim and N.K. Ali
The purpose of this paper is to describe a very low‐cost way to prepare Ge nano/microstructures by means of filling the material inside porous silicon (PS) using a conventional…
Abstract
Purpose
The purpose of this paper is to describe a very low‐cost way to prepare Ge nano/microstructures by means of filling the material inside porous silicon (PS) using a conventional and cost effective technique in which thermal evaporator with PS acts as patterned substrate. Also, the potential metal‐semiconductor‐metal (MSM) photodetector IV characteristics of the structure are demonstrated.
Design/methodology/approach
PS was prepared by anodization of Si wafer in ethanoic hydrofluoric acid. The Ge layer was then deposited onto the PS by thermal evaporation. The process was completed by Ni metal deposition using thermal evaporator followed by metal annealing of 400°C for 10 min. Structural analysis of the samples was performed using energy dispersive X‐ray analysis (EDX), scanning electron microscope (SEM), X‐ray diffraction (XRD) and Raman spectroscopy.
Findings
A uniform circular network distribution of pores is observed with sizes estimation of 100 nm to 2.5 μm by SEM. Also observed are clusters with near spherical shape clinging around the pores believed to be Ge or GeO2. The EDX spectrum suggests the presence of Ge or GeO2 on and inside the pore structure. Raman spectrum showed that good crystalline structure of the Ge can be produced inside the silicon pores. XRD showed the presence of a Ge phase with the diamond structure by (111), (220), and (400) reflections. Finally, current‐voltage (I‐V) measurement of the Si/Ge/PS MSM photodetector was carried out. It showed lower dark currents compared to control device of Si. The device showed enhanced current gain compared to conventional Si device which can be associated with the presence of Ge nanostructures in the PS.
Originality/value
This paper shows that it is possible to grow Ge nano/microstructure on PS by using a simple and low‐cost method of thermal evaporation and thermal annealing and demonstrates potential MSM photodetector IV characteristics from the device.
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Jian‐hong Yang, Ying Wei, Xue‐yuan Cai and Jin‐zhi Ran
The paper aims to investigate the influences of the tensile strain and the threading dislocations (TDs) in the germanium (Ge) epitaxial layer on the performance of the Ge vertical…
Abstract
Purpose
The paper aims to investigate the influences of the tensile strain and the threading dislocations (TDs) in the germanium (Ge) epitaxial layer on the performance of the Ge vertical p‐i‐n photodetectors on Si substrate.
Design/methodology/approach
The dark current, photo responsivity and time responsivity of detector were calculated using two‐dimensional drift‐diffusion device modeling and compared with experimental data.
Findings
The incorporation of the tensile strain and the reduction of the TDs in the Ge epilayer can increase the performance of the detector.
Originality/value
An optical design of detector is suggested with lower TD in the Ge buffer layer, which can exhibit superior performance.
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Z.‐M. Li, K.‐W. Chai, S.P. McAlister and J. Simmons
We have implemented a two‐dimensional (2D) time‐dependent hydrodynamic model suitable for studying III‐V heterostructural semiconductor devices. This we apply in simulating a…
Abstract
We have implemented a two‐dimensional (2D) time‐dependent hydrodynamic model suitable for studying III‐V heterostructural semiconductor devices. This we apply in simulating a heterojunction metal‐semiconductor‐metal (MSM) photodetector subject to pico‐second optical pulses. The inclusion of the energy balance equation introduces an additional time delay in the response of the detector, which is comparable to the energy relaxation time.
Alireza Erfanian, Hamed Mehrara, Mahdi Khaje and Ahmad Afifi
– The purpose of this paper is to demonstrate a successful fabrication of 2 × 128 linear array of typical infrared (IR) detectors made of p-type tSi/porous Si Schottky barrier.
Abstract
Purpose
The purpose of this paper is to demonstrate a successful fabrication of 2 × 128 linear array of typical infrared (IR) detectors made of p-type tSi/porous Si Schottky barrier.
Design/methodology/approach
Using metal-assisted chemical etching (MaCE) as a unique approach, a sample definition of a porous Si nanostructure region for fabricating of any high-density photodetectors array has been formulated. Besides, the uniformity of pixels at different position along the array has been confirmed by optical images and measurements of photocurrent in IR regime at room temperature.
Findings
The experimental result illustrates the existence of an open-circuit voltage up to 30 mV at 1.5-μm wavelength for an area of 50 × 50 μm2. Additionally, this behavior is almost the same at different pixels of fabricated array.
Research limitations/implications
The uniformity of pixels and definition of nanostructure region are two most important challenges in fabrication of any high-density photodetectors array.
Practical implications
MaCE guarantees formation of reproducible, high-fidelity and controllable nanometer-size porous Si with well-defined and sharp edges of the patterned areas.
Originality/value
The proposed method offers a low-cost and simple process to fabricate high-density arrays of Schottky detectors which are compatible with the complementary metal-oxide semiconductor process.
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