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The Sb-doped ZnO films were grown on c-plane sapphire by metal organic chemical vapor deposition technology with various substrate temperatures. We have examined the influence of the substrate temperature on the crystal, electrical and optical properties of the Sb-doped ZnO films. The XRD patterns indicated the undoped ZnO film and the Sb-doped ZnO films showed a strong preferred orientation toward the c-axis. Hall effects measurements revealed the Sb-doped ZnO films exhibited p-type electrical conductivity. Low temperature photoluminescence spectra confirmed the existence of Sb in ZnO films. The photoluminescence spectra of the Sb-doped ZnO films revealed the transition between the free electrons and acceptors peak at 3.243 eV, the acceptor-bound exciton peak at 3.319 eV. The thermal binding energy of the Sb accepter was estimated to be about 0.19 eV. [ABSTRACT FROM AUTHOR]

ZnO nanostructures are grown on Si and GaAs substrates by chemical bath deposition (CBD) method. Scanning electron microscope (SEM) measurements indicate that ZnO nanorods are formed on Si substrate, in contrast to the nanorods, network ZnO nanowalls are obtained on GaAs substrate. To elucidate the mechanism of ZnO nanostructures grown by CBD method, the morphology evolution mechanisms of the ZnO with growth time and solution concentration nanostructures are investigated systematically. A corresponding growth model from the view of crystal nucleation and growth process is proposed. The understanding of morphology evolution of ZnO nanostructures on different substrates will facilitate the controllable growth of ZnO nanostructures and therefore crucial for the application of ZnO nanodevices. [ABSTRACT FROM AUTHOR]

N-ZnO/GaO/ p-GaN heterojunction light-emitting diode (LED) was fabricated by metal-organic chemical vapor deposition. Compared with the n-ZnO/ p-GaN structure, the deep level visible emission at 525 nm was completely suppressed while UV emission at ~392 nm was significantly improved in ZnO/GaO/ p-GaN structure. The role of GaO in n-ZnO/GaO/ p-GaN heterojunction LED was discussed in detail. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV)-emitting n-ZnO/SiO/ p-GaN devices were fabricated by metalorganic chemical vapor deposition. Electroluminescence spectra of the devices were measured from both the n-ZnO and p-GaN sides. It was found that a narrow emission peak centered at ∼391.3 nm was observed from the front side, while three peaks (372 nm, 380 nm, and 390 nm) emerged in the case of testing from the GaN side. To interpret this notable difference, a theoretical mechanism is proposed based on carrier accumulation and injection under forward bias voltage. [ABSTRACT FROM AUTHOR]

Abstract: Al-doped ZnO (AZO) transparent conductive thin films have been prepared by radio-frequency magnetron sputtering with a ceramic target (98 wt.% ZnO, 2 wt.% Al2O3) in different Ar+H2 ambient at a substrate temperature of 200 °C. To investigate the influence of H2-flow on the properties of AZO films, H2-flow was changed during the growth process with a fixed Ar-flow of 60 sccm. The results indicate that H2-flow has a considerable influence on the transparent conductive properties of AZO films. The low resistivity in the order of 10−4 Ω cm and the high average transmittance more than 92% in the visible range were obtained for the samples prepared in the optimal H2-flow range from 0.4 sccm to 1.0 sccm. In addition, the influence of H2-flow on the structure and composition of AZO films have also been studied. [Copyright &y& Elsevier]

Abstract: ZnO films were grown on GaAs(001)substrates at different surface treatment conditions at different growth temperatures by metal-organic chemical vapor deposition. ZnO(100) and ZnO(002) films that had different preferred orientations were grown according to different chemical etching condition. The crystallinity and optical properties of ZnO films were investigated with X-ray diffraction and the room-temperature photoluminescence spectra. Compared with ZnO(002) films, ZnO(100) films that have undergone variation at the preferred orientation have better crystal structure. Moreover, all samples have similar optical characteristics at the same growth temperature. For GaAs substrates etched under different conditions, the analysis results of X-ray photoelectroscopy show that the preferred orientation variations of ZnO films take place because rich As layer are formed in process of chemical etching. [Copyright &y& Elsevier]

ZnO films were successfully deposited on c-plane sapphire substrates by low-pressure MOCVD using Diethylzinc (DEZn) and oxygen. The c-axis oriented ZnO films were grown on sapphire at the temperature of 600°C with different ZnO buffer layer thicknesses between 5 and 55 nm. The effects of ZnO buffer layer on crystallinity, surface morphology and optical properties of ZnO films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) spectrum, respectively. It was found that surface morphology, structural and optical properties of the films depended on the thickness of the buffer layer. The ZnO film grown on the 15 nm thick ZnO buffer layer shows a flat and dense surface, the good structural and optical properties. [Copyright &y& Elsevier]

The ZnO films were deposited on (0 0 1)Si substrate by metal-organic chemical vapor deposition (MOCVD). Annealing was performed in air for 60 min at 800°C. The X-ray diffraction patterns of the samples showed sharp diffraction peaks for ZnO(0 0 2), which indicated that the films were highly c-axis oriented. Zn and O elements in the as-deposited ZnO film were investigated and compared with those in the annealed ZnO film by using X-ray Photoelectron Spectroscopy (XPS). XPS spectra showed that ZnO films changed from Zn-rich to O-rich after being annealed. [Copyright &y& Elsevier]

The light-emitting diode of p-ZnO/n-GaAs heterojunction was grown by metal-organic chemical vapor deposition. The p-ZnO films have been formed by the doping As atoms which diffuse into ZnO film from GaAs substrate. The p-type behavior of As-doped ZnO films based on As-doped p-ZnO/n-GaAs, p-ZnO/p-GaAs heterojunction was studied by carrying out I-V measurements and x-ray photoelectron spectroscopy. The I-V characteristic of p-ZnO/n-GaAs heterojunction showed characteristic of rectifying diode and visual-infrared electroluminescence emission under forward current injection at room temperature. The I-V of the heterounction had a threshold voltage of ∼2.5 V. [ABSTRACT FROM AUTHOR]

Vertically aligned ZnO nanowall networks were grown on p-GaN/sapphire substrates by metal-organic chemical vapor deposition, and further heterojunction light-emitting diodes based on n-ZnO/p-GaN were fabricated. Highly efficient ultraviolet-blue emission was observed from the diode under forward bias, and it operated continuously for 8.5 h with decay of only 8.08% under a continuous current of 12 mA. The diode exhibited low emission onset and good stability. In addition, temperature-dependent electroluminescence and current-voltage behaviors of the diode were investigated to examine the thermal effects on light output power, spectral line shift, and temperature sensitivity of the resulting voltage. [ABSTRACT FROM AUTHOR]

We fabricated the Ultraviolet light-emitting diode (LED) based on n-ZnO/i-NiO/p-Si heterostructure by metal-organic chemical vapor deposition (MOCVD). The device exhibited diode-like rectifying characteristics with a turn-on voltage of 3.2 V. The NiO film with high resistance state and [200] preferred orientation acted as an electron blocking layer, which produced a larger ZnO/NiO conduction band offset of 2.93 eV than that of ZnO/Si (0.30 eV). Under forward bias, prominent ultraviolet emissions peaked around 375 nm accompanying with rather weak blue–white emissions peaked around 480 nm were observed at room temperature. Furthermore, the mechanism of the electroluminescence was tentatively discussed in terms of the band diagram of the diode. [ABSTRACT FROM AUTHOR]

We fabricated a p-NiMgO:Li/MgO/n-ZnO NWs/ITO heterojunction device and studied its electroluminescence characteristics. Emission from n-ZnO was observed under forward biases. Significantly the random lasing was achieved. Besides, to investigate the characteristics of NiMgO:Li material, we carried out a comparative study on NiMgO:Li and NiO:Li. The p-NiMgO:Li thin films were deposited on c-sapphire substrates by radio-frequency magnetron sputtering using high-purity NiO and MgO ceramic targets. Although, the hole concentration of NiMgO:Li thin film was low compared with the NiO:Li thin film, the electronic mobility and the optical transmittance have obviously improvements. [ABSTRACT FROM AUTHOR]

Xenon gas and mercury vapor based broad spectrum light sources have wide application, however, are hard to compact. On the contrary, LEDs are easy for compaction, but are hard to emit a broad spectrum. In this work, we demonstrate a simple phosphor free LED structure of ZnO/MgO/ITO, of which the spectrum covers the range from 300 to 650 nm. The device was fabricated on commercially available ITO substrate, and the ZnO/MgO structure was successively grown by MOCVD method, of which the morphology, crystallinity and optical quality were characterized. A thin MgZnO layer with graded composition is believed to form through the miscibility of MgO and ZnO during the initial growth stage of ZnO. The active region of the device includes the thin MgZnO layer and part of the subsequent grown ZnO layer. The light with wavelength shorter than ~360 nm is attributed to the near band edge emission of the MgZnO layer. And the near band edge emission and deep level emissions of ZnO contribute to the spectrum from ~360 to 650 nm. The working mechanism of the device is discussed mainly based on the energy band diagram. [ABSTRACT FROM AUTHOR]

We fabricated the light-emitting diodes (LEDs) consisting of n-ZnO/p-NiO/p-Si heterostructure by using metal-organic chemical vapor deposition (MOCVD) combined with radio frequency (RF) magnetron sputtering. The devices exhibited diode-like rectifying current–voltage characteristics and had a turn-on voltage of 6.8 V. Under forward bias, a prominent broad emission peaked around 400–650 nm was observed at room temperature. The asymmetric electroluminescence (EL) spectra were consisted of two apparent bands, which located at 420 and 495 nm corresponding to the violet and green luminescence, respectively. Furthermore, the mechanism of the light emission was tentatively discussed in terms of the band diagrams of the heterojunction. [ABSTRACT FROM AUTHOR]

Ultraviolet light-emitting diodes (LED) based on n-ZnO/NiO/p-GaN were realized by metal-organic chemical vapor deposition (MOCVD). The devices exhibited diode-like rectifying current–voltage characteristics and had a turn-on voltage of 7.5 V. High quality NiO film as an electron blocking layer inserted between the ZnO and GaN films showed high resistance state with preferred [1 1 1] orientation, which produced a larger ZnO/NiO conduction band offset of 2.93 eV than that of ZnO/GaN (0.15 eV). The electroluminescence spectra of the n-ZnO/i-NiO/p-GaN heterostructure demonstrated that electrons were effectively confined in the ZnO active region, and thus leading to the enhancement of the excitonic emission from the ZnO side. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, n-ZnO single microwire/p+-Si heterojunction LEDs are fabricated using the transparent conductive ITO film as an electrode. A distinct UV emission resulting from free exciton recombination in a ZnO single microwire is observed in the electroluminescence. Size difference of ZnO single microwire shows significant influence on emission efficiency. The EL spectra of n-ZnO single microwire/p-Si heterostructure exhibited relatively stronger UV emission which was compared with the EL spectra of n-ZnO single nanowire/p-Si heterostructure and n-ZnO film/p-Si heterostructure, respectively. [Copyright &y& Elsevier]

Highlights: [•] 1D ZnO rods with wide size range are achieved by control the seed layers thickness using chemical bath deposition. [•] Remarkable morphology change occurred with the increase of seed layers thickness from 12nm to 98nm. [•] The length of 1D the ZnO rods decreased from 13.1μm to 2.1μm, meanwhile the diameter decreased from 2.4μm to 102nm. [•] The laying 1D ZnO rods standup gradually. [•] The near band edge emission in the PL spectra of the ZnO rods shows a blueshift to higher energy direction. [ABSTRACT FROM AUTHOR]

Abstract: The n-ZnO/i-NiO/n-GaN isotype heterojunction diode was fabricated by metal organic chemical vapor deposition (MOCVD) on the n-GaN/sapphire substrate. The current–voltage (I–V) measurement showed typical rectification characteristics with a turn-on voltage of 2.5V. An ultraviolet emission peak around 363nm was observed from the EL spectra at room temperature. High ultraviolet light extraction efficiency was proved by a superlinear curve of the intensity ratio of ultraviolet to visible emission. The mechanism of electroluminescence has been tentatively elucidated in terms of band diagrams of the heterojunction. [Copyright &y& Elsevier]

Abstract: In this study, we have prepared ZnO nanorods on cracked GaN substrates using aqueous solution method. Unique electrical characterization of one individual lying ZnO nanorod is analyzed by conductive atomic force microscopy (C-AFM). Effect of anisotropy properties on the conductivity of a single nanorod has been investigated. The current maps of ZnO nanorods have been simultaneously recorded with the topography which is gained by AFM-contact mode. The C-AFM measurement present local current–voltage (I–V) characteristics of the side facets of one individual lying nanorod, however, no current is detected on the top facets of ZnO nanorods. Measurement results indicate that the side facets are more electrically active than the top facets of ZnO nanorods due to lower Schottky barrier height of the side facets. [Copyright &y& Elsevier]

Abstract: N-doped ZnO (ZnO:N) films are grown by a low-pressure plasma assisted metal-organic chemical vapor deposition system on insulating Si (111) substrate. N2O plasma is used as the N precursor of ZnO:N films, which is activated by a radio frequency generator. The influence of activating power on the properties of ZnO films is studied by means of X-ray diffraction, Hall effect, X-ray photoelectron spectroscopy and low temperature photoluminescence measurements. P-type ZnO:N films with acceptable electrical and optical properties are achieved under the optimal activating power conditions. XPS study reveals a competition between acceptor NO and donor (N2)O during doping influence the properties of ZnO films. [Copyright &y& Elsevier]

Abstract: ZnO-based heterojunction light emitting diodes (LEDs) with MgZnO barrier layer had been fabricated on the p-Si substrate by metal-organic chemical vapor deposition (MOCVD) technology. The current–voltage (I–V) characteristics exhibited a typical p–n diode behavior. Both ultraviolet (UV) and visible emissions could be detected in the electroluminescence (EL) measurement. The result was compared with the EL spectrum of n-ZnO/p-Si heterojunction LED without MgZnO barrier layer. An improved light extraction efficiency by about 31% was realized owing to the current-blocking effect of MgZnO layer. The result indicated that MgZnO barrier layer can prevent the electrons as expected and realize electron–hole recombination in ZnO layer effectively. [Copyright &y& Elsevier]

Abstract: A p-ZnO:N/n-GaN:Si structure heterojunction light-emitting diode (LED) is fabricated on c-plane sapphire by full metal organic chemical vapor deposition (MOCVD) technique. The p-type layer with hole concentration of 8.94×1016 cm−3 is composed of nitrogen-doped ZnO using NH3 as the doping source with subsequent annealing in N2O plasma ambient. Silicon-doped GaN film with electron concentration of 1.15×1018 cm−3 is used as the n-type layer. Desirable rectifying behavior is observed from the current–voltage (I–V) curve of the device. The forward turn on voltage is about 4V and the reverse breakdown voltage is more than 7V. A distinct ultraviolet (UV) electroluminescence (EL) with a dominant emission peak centered at 390nm is detected at room temperature from the heterojunction structure under forward bias conditions. The origins of the EL emissions are discussed in comparison with the photoluminescence (PL) spectra. [Copyright &y& Elsevier]

Abstract: In this paper, we proposed a new p-type ZnO doping method with metal organic chemical vapor deposition (MOCVD) technology by inserting a GaAs interlayer between substrate and ZnO epitaxial layer. The doping concentration of p-type ZnO film is able to be controlled by adjusting the thickness of the GaAs interlayer. With this method, we fabricated n-ZnO/p-ZnO:As homojunction light-emitting diode (LED) on ITO-glass substrate pre-coated with 20nm GaAs interlayer. The device exhibits a typical rectifying behavior by current–voltage (I–V) measurement. When the device is forward biased, UV–vis electroluminescence (EL) emissions can be observed clearly. [Copyright &y& Elsevier]

Abstract: Heterojunction light-emitting diodes with ZnO/Si structure were fabricated on both high-resistivity (p) and low-resistivity (p+) Si substrates by metal–organic chemical vapor deposition technology. Fairly good rectifications were observed from the current–voltage curves of both heterojunctions. Ultraviolet (UV) and blue-white electroluminescence (EL) from ZnO layer were observed only from ZnO/p+-Si heterojunction under forward bias at room temperature (RT), while strong infrared (IR) EL emissions from Si substrates were detected from both ZnO/p-Si and ZnO/p+-Si heterojunctions. The UV and IR EL mechanisms have been explained by energy band structures. The realization of RT EL in UV–visible and IR region on Si substrate has great applicable potential for Si-based optoelectronic integrated circuits. [Copyright &y& Elsevier]