Ultraviolet electroluminescence of ZnO based heterojunction light emitting diode (EI CONFERENCE)
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A heterostructured ZnO:Al/n-ZnO/p-GaN transparent electrode lighting-emitting diode was fabricated using n-ZnO and p-GaN materials.The structure and electroluminescence properties of ZnO nanorods were characterized by SEM,TEM and fluorescence spectrum.The properties and mechanism of electroluminescence were measured and analyzed by semiconductor parameter system and spectrometer.The result shows that ZnO:Al/n-ZnO/p-GaN device could emit effective blue-violet electroluminescence which is originated from n-ZnO,p-GaN and interface emission,in addition,adopting ZnO:Al as the transparent electrode can improve the light extraction efficiency of the light-emitting diode.The heterojunction can be applied in the field of high efficiency shortwavelength light-emitting device.
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We have demonstrated that fabrication of the ZnO nanowire/GaN hetero-junction light emitting diode (LED) by contacting the tip of the ZnO nanowires with the GaN film, and UV electroluminescence from the p-n junction. In this study, we fabricated the heterojunction by directly-growth of the ZnO nanowires on the GaN film using nanoparticleassisted pulsed laser deposition. Photoluminescence spectrum of the ZnO nanowires showed a weak near-band-edge ultraviolet (UV) emission and a visible broad emission, which was related to transition by ZnO defect state. We applied a selective laser irradiation to the p-n junction of the ZnO-based LED. The UV emission was strongly enhanced from the laser-irradiated p-n junction.
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Heterostructure light-emitting diodes(LEDs)were fabricated by growing ZnO nanorods and undoped ZnO films on p-GaN templates.The heterojunction showed a diode-like I–V characteristic and emitted electroluminescence(EL)peaks at 383 nm,402 nm,438 nm,and 507 nm under forward bias.Since the electrons from ZnO nanorods and the holes from p-GaN could be injected into ZnO films with a relatively low carrier concentration and mobility,the radiative recombination was mainly confined in the ZnO film region.As a result,the ZnO nanorods/i-ZnO/p-GaN light emitting diode exhibits a stronger ultraviolet–violet emission peak.
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Wide-bandgap semiconductor
Ultraviolet
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White-light-emitting diode (LED) with effective energy conservation and long service life could be employed in numerous applications. In this study, the high-performance n-ZnO films were first prepared via pulsed laser deposition on p-GaN substrates and then the n-ZnO/p-GaN heterojunction LED was fabricated. This LED exhibits blue and yellow light emission, and their emission intensities can be tuned by adjustment of the fabrication parameters (e.g. oxygen pressure) and/or by introduction of a semi-insulating i-ZnO layer to form a p-GaN/i-ZnO/n-ZnO heterojunction. Thus, a facile approach has been proposed for the preparation of white LED.
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Abstract ZnO/GaN p‐i‐n heterojunctions light emitting diodes were fabricated by plasma‐assisted molecular beam epitaxy. We make use of high resistivity of nitrogen doped ZnO to fabricate n‐ZnO/i‐ZnO/p‐GaN heterojunction light emitting diode. The emission of i‐ZnO was obtained due to the limitation effect of i‐ZnO on electrons and holes. Moreover, n‐ZnO/i‐MgO/p‐GaN heterojunction light emitting diode was also fabricated. The limitation effect on electrons is increased in this heterojunction. The bright ultraviolet electroluminescence at 382 nm originating from the ZnO layer was observed in the room temperature electroluminescence spectrum. We hope to realize the stimulated emission of ZnO using these heterojunctions by the improvement of crystal quality and the optimization of device structure. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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ZnO-based heterojunction light-emitting diodes have been fabricated on p-type GaAs substrate by plasma-assisted molecular beam expitaxy. An electron-blocking MgO layer between thin ZnO film and p-GaAs substrate plays a key role in improving performance of the diodes. Comparing with the n-ZnO/p-GaAs heterojunction, the ZnO/MgO/p-GaAs heterojunction shows a typical diode characteristic with a forward threshold voltage of 3 V. Electroluminescence measurement indicates that the ZnO/MgO/p-GaAs heterojunction has a visible emission band attributed to the defect-related recombination in the ZnO layer and an ultraviolet emission peak.
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Zinc oxide (ZnO) is a wide-bandgap material with excellent optical properties for optoelectronics applications. ZnO nanostructures are attractive for research because it is easy to fabricate in single-crystalline form and it has interesting physical properties at the nanoscale. In this paper, we report our successful growth of a p-type ZnO nanorods/n-GaN film heterojunction ultraviolet light-emitting diode (LED). The heterojunction LED shows its advantages over a p-ZnO film/n-GaN film heterojunction. The LED demonstrates a rectifying I–V characteristics with a turn-on voltage of 2.7 V. The ideality factor is 6.5. The existences of interface charges in the interface are the reason for this low turn-on voltage and high ideality factor in the heterojunction. Electroluminescence (EL) spectra of the LED consist of an ultraviolet peak at 378 nm and a broad yellow emission centered at 560 nm. Fitting and comparing EL of the LED with PL of p-ZnO and n-GaN show that p-ZnO contributes more to the EL than n-GaN.
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The ZnO/n+-Si heterojunction has been fabricated via depositing nominally undoped ZnO film by reactive sputtering on a heavily arsenic-doped (n+) silicon substrate. The sputtered ZnO film was n-type in conductivity with an electron concentration of 1.0×1018 cm-3. The current-voltage characteristics indicate that the ZnO/n+-Si heterojunction does not possess rectifying function. Under the forward bias with the negative voltage applied on the n+-Si substrate, the heterojunction emits ultraviolet and broad visible lights characteristics of near-band-edge and defect-related emissions of ZnO, respectively. The EL mechanism has been tentatively explained in terms of the energy-band diagram.
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Ultraviolet
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