Fabrication and Characterization of ZnO Nanorods Based Intrinsic White Light Emitting Diodes (LEDs) PDF Download
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Author: Nargis Bano
Publisher:
ISBN: 9789173930543
Category :
Languages : en
Pages : 68
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Author: Nargis Bano
Publisher:
ISBN: 9789173930543
Category :
Languages : en
Pages : 68
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Book Description
Author: Chi-man Luk
Publisher:
ISBN:
Category : Semiconductors
Languages : en
Pages : 190
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Book Description
With the optimized growth parameters, n-ZnO:Al/i-ZnO/p-GaN:Mg heterojunction LEDs were fabricated. The electrical characteristics of the diodes were investigated. The ultraviolet (UV) electroluminescence (EL) from the device was detected at room temperature. The emission is attributed to the electron-hole radiative recombination in the ZnO region and is explained in detail by an energy band diagram. ZnO nanostructures are expected to have improved optical and electronic properties because of the quantum confinement effect. Using low-temperature aqueous chemical method, the ZnO nanorods arrays were grown on the buffer layers prepared at various temperatures. The nanorods were grown along [0001] direction. The PL measurement indicated that the emission spectrum covered a UV peak at ~ 380 nm and a broad visible band at ~ 560 nm. The PL spectra of the ZnO nanorods are independent on the growth temperature of the buffer layer. Moreover, the buffer-layer-thickness-dependent structural and optical properties were studied. The as-grown ZnO nanorods were utilized to fabricate hybrid LED with an organic semiconductor, N, N'-diphenyl-N, N'-bis(1-naphthyl)-1, 1'-biphenyl-4, 4'-diamine (?NPD), which is one of the most widely used hole transport and blue-emitting organic semiconductors. Current-voltage characteristics of the devices exhibited nonlinear rectifying behaviour. The EL spectra of the hybrid LEDs reveal a blue and broad yellowish green emission originated from the?NPD layer and the defect levels of the ZnO respectively. The origin of the emission bands from the hybrid structures will be examined.
Author: Leelaprasanna Mandalapu Jayaramulu
Publisher:
ISBN:
Category : Optoelectronic devices
Languages : en
Pages : 314
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Author: Yu-Lin Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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ABSTRACT: Hydrogen effects on the electrical and optical properties of p-i-n ZnO light emitting diodes (LEDs) were investigated. There were no diode characteristics or light emission observed from p-i-n ZnO LEDs unless the LEDs were annealed at 350 °C after fabrication. Annealed diodes showed band-edge electroluminescence at 385nm and a broad defect band with a peak at 930nm at room temperature. The effects of hydrogen plasma, moisture, water, and phosphoric acid solution on the annealed diode characteristics were investigated and significant degradation of electrical and optical properties were observed in all cases. The plasma-enhanced chemical vapor-deposited (PECVD) SiO2 and SiN[subscript x] passivation effects on p-i-n ZnO LEDs were also investigated.
Author: Abdul Samad Syed
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659189814
Category :
Languages : en
Pages : 84
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Fabrication of efficient Ultraviolet Light Emitting Diodes (UV LEDs) is a challenging task for the semiconductor industry of the modern times. Finding the suitable semiconducting material is the key in order to make efficient LEDs. This book aims at understanding the use of ZnO in UV LEDs that demands the understanding of its optical properties first. Structural and optical properties of any semiconducting material are strongly correlated. An adequate knowledge and understanding of this relationship is necessary for fabrication of devices with desired optical properties. The aim of this work was to investigate the change in optical properties caused by growth techniques and substrate modification. To study the influence of growth technique on optical properties, ZnO nanostructures were grown using atmospheric pressure metal organic chemical vapor deposition (APMOCVD) and chemical bath deposition (CBD) techniques. Off-cut angle of SiC substrates were modified to observe the change on the optical properties. The results that are obtained demonstrate a significant contribution in the fields of ZnO based nano-optoelectronics and nano-electronics.
Author: Hyun-Sik Kim
Publisher:
ISBN:
Category :
Languages : en
Pages :
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ZnO-based light emitting diodes were fabricated on c-plane sapphire using ZnO:P/ Zn[subscript 0.9]Mg[subscript 0.1]O/ZnO/ Zn[subscript 0.9]Mg[subscript 0.1]O/ZnO:Ga p-i-n heterostructures. The p-i-n heterojunction diodes are rectifying and show light emission under forward bias. The electroluminescence spectra shows deep level emission at low bias, but near band edge ultraviolet emission at high voltage bias. A decrease in leakage currents in as-fabricated structures was achieved via low temperature oxygen annealing.
Author: Chi-Hang Cheung
Publisher:
ISBN: 9781361117651
Category :
Languages : en
Pages :
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Author: Ka-kuen Leung
Publisher:
ISBN:
Category : Gallium nitride
Languages : en
Pages : 372
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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By 2015, the US Department of Energy has set as a goal the development of advanced solid state lighting technologies that are more energy efficient, longer lasting, and more cost-effective than current technology. One approach that is most attractive is to utilize light-emitting diode technologies. Although III-V compound semiconductors have been the primary focus in pursuing this objective, ZnO-based materials present some distinct advantages that could yield success in meeting this objective. As with the nitrides, ZnO is a direct bandgap semiconductor whose gap energy (3.2 eV) can be tuned from 3.0 to 4 eV with substitution of Mg for higher bandgap, Cd for lower bandgap. ZnO has an exciton binding energy of 60 meV, which is larger than that for the nitrides, indicating that it should be a superior light emitting semiconductor. Furthermore, ZnO thin films can be deposited at temperatures on the order of 400-600 C, which is significantly lower than that for the nitrides and should lead to lower manufacturing costs. It has also been demonstrated that functional ZnO electronic devices can be fabricated on inexpensive substrates, such as glass. Therefore, for the large-area photonic application of solid state lighting, ZnO holds unique potential. A significant impediment to exploiting ZnO in light-emitting applications has been the absence of effective p-type carrier doping. However, the recent realization of acceptor-doped ZnO material overcomes this impediment, opening the door to ZnO light emitting diode development In this project, the synthesis and properties of ZnO-based pn junctions for light emitting diodes was investigated. The focus was on three issues most pertinent to realizing a ZnO-based solid state lighting technology, namely (1) achieving high p-type carrier concentrations in epitaxial and polycrystalline films, (2) realizing band edge emission from pn homojunctions, and (3) investigating pn heterojunction constructs that should yield efficient light emission. The project engaged established expertise at the University of Florida in ZnO film growth (D. Norton), device fabrication (F. Ren) and wide bandgap photonics (S. Pearton). It addressed p-type doping and junction formation in (Zn, Mg)O alloy thin films. The project employed pulsed laser deposition for film growth. The p-type dopant of interest was primarily phosphorus, given the recent results in our laboratory and elsewhere that this anions can yield p-type ZnO-based materials. The role of Zn interstitials, oxygen vacancies, and/or hydrogen complexes in forming compensating shallow donor levels imposes the need to simultaneously consider the role of in situ and post-growth processing conditions. Temperature-dependent Hall, Seebeck, C-V, and resistivity measurements was used to determine conduction mechanisms, carrier type, and doping. Temperature-dependent photoluminescence was used to determine the location of the acceptor level, injection efficiency, and optical properties of the structures. X-ray diffraction will used to characterize film crystallinity. Using these materials, the fabrication and characterization of (Zn, Mg)O pn homojunction and heterojunction devices was pursued. Electrical characterization of the junction capacitance and I-V behavior was used to extract junction profile and minority carrier lifetime. Electroluminescence from biased junctions was the primary property of interest.
Author: Zhe Chuan Feng
Publisher: Taylor & Francis
ISBN: 1439855757
Category : Science
Languages : en
Pages : 563
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Book Description
Through their application in energy-efficient and environmentally friendly devices, zinc oxide (ZnO) and related classes of wide gap semiconductors, including GaN and SiC, are revolutionizing numerous areas, from lighting, energy conversion, photovoltaics, and communications to biotechnology, imaging, and medicine. With an emphasis on engineering a
