ZnO nanostructures for optoelectronics: Material properties and device applications

Exploiting the low spatial coherence of specifically designed random lasers, researchers demonstrate speckle-free full-field imaging in the regime of intense optical scattering. Their results show that the quality of images generated from random-laser illumination is superior to those generated from spatially coherent illumination.

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Speckle-free laser imaging using random laser illumination

Zinc oxide (ZnO), with its excellent luminescent properties and the ease of growth of its nanostructures, holds promise for the development of photonic devices. The recent advances in growth of ZnO nanorods are discussed. Results from both low temperature and high temperature growth approaches are presented. The techniques which are presented include metal?organic chemical vapour deposition (MOCVD), vapour phase epitaxy (VPE), pulse laser deposition (PLD), vapour?liquid?solid (VLS), aqueous chemical growth (ACG) and finally the electrodeposition technique as an example of a selective growth approach. Results from structural as well as optical properties of a variety of ZnO nanorods are shown and analysed using different techniques, including high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), photoluminescence (PL) and cathodoluminescence (CL), for both room temperature and for low temperature performance. These results indicate that the grown ZnO nanorods possess reproducible and interesting optical properties. Results on obtaining p-type doping in ZnO micro-?and nanorods are also demonstrated using PLD. Three independent indications were found for p-type conducting, phosphorus-doped ZnO nanorods: first, acceptor-related CL peaks, second, opposite transfer characteristics of back-gate field effect transistors using undoped and phosphorus doped wire channels, and finally, rectifying I?V characteristics of ZnO:P nanowire/ZnO:Ga p?n junctions. Then light emitting diodes (LEDs) based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed. The hybrid LEDs reviewed and discussed here are mainly presented for two groups: those based on n-ZnO nanorods and p-type crystalline substrates, and those based on n-ZnO nanorods and p-type amorphous substrates. Promising electroluminescence characteristics aimed at the development of white LEDs are demonstrated. Although some of the presented LEDs show visible emission for applied biases in excess of 10 V, optimized structures are expected to provide the same emission at much lower voltage. Finally, lasing from ZnO nanorods is briefly reviewed. An example of a recent whispering gallery mode (WGM) lasing from ZnO is demonstrated as a way to enhance the stimulated emission from small size structures.

https://iopscience.iop.org/article/10.1088/0957-4484/20/33/332001/pdf

Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers.

ZnO is a material which is of great interest for a variety of applications due to its unique properties and the availability of a variety of growth methods resulting in a number of different morphologies and a wide range of material properties of synthesized nanostructures. In this review, we will discuss recent advances in important and/or controversial issues concerning ZnO properties and its applications. We will also discuss areas where further improvements are needed, and in particular discuss the issues related to the environmental stability of ZnO and its implications on reproducibility of measurements and the toxicity of ZnO nanomaterials.

ZnO nanostructures: growth, properties and applications

Ultraviolet semiconductor lasers are widely used for applications in photonics, information storage, biology and medical therapeutics. Although the performance of gallium nitride ultraviolet lasers has improved significantly over the past decade, demand for lower costs, higher powers and shorter wavelengths has motivated interest in zinc oxide (ZnO), which has a wide direct bandgap and a large exciton binding energy. ZnO-based random lasing has been demonstrated with both optical and electrical pumping, but random lasers suffer from reduced output powers, unstable emission spectra and beam divergence. Here, we demonstrate electrically pumped Fabry-Perot type waveguide lasing from laser diodes that consist of Sb-doped p-type ZnO nanowires and n-type ZnO thin films. The diodes exhibit highly stable lasing at room temperature, and can be modelled with finite-difference time-domain methods.

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Electrically pumped waveguide lasing from ZnO nanowires

The electrically pumped ultraviolet (UV) random lasing in c-axis oriented ZnO polycrystalline films has been demonstrated. For this demonstration, a metal-oxide-semiconductor structure of Au∕SiOx(x<2)∕ZnO film was fabricated on a silicon substrate. With ever-higher forward bias where the negative voltage was connected to the silicon substrate, the UV electroluminescence from such a ZnO-based device transformed from the spontaneous emission to the random lasing in the ZnO film. It is believed that the recurrent scattering and interference of the enough strong electroluminescent UV light in the in-plane random cavities formed in the ZnO film leads to electrically pumped UV random lasing.

Electrically pumped ZnO film ultraviolet random lasers on silicon substrate

We report the electrically pumped ultraviolet random lasing from ZnO nanorod arrays on Si. Metal-insulator-semiconductor structures in a form of Au/SiO2/ZnO-nanorod-array were fabricated on Si. Such devices exhibit random lasing when the Au electrode is applied with a sufficiently high positive voltage. In this context, in the region adjacent to SiO2/ZnO-nanorod-array interface, stimulated emission from ZnO occurs due to population inversion and, moreover, light is scattered by the nanorods and SiO2 films. Therefore, random lasing proceeds due to optical gain achieved by the stimulated emission and multiple scattering.

Room temperature electrically pumped ultraviolet random lasing from ZnO nanorod arrays on Si.

ZnO:Eu thin-films: Sol–gel derivation and strong photoluminescence from 5D0 → 7F0 transition of Eu3+ ions

Optical properties of sputtered hexagonal CdZnO films with band gap energies from 1.8 to 3.3 eV

Carbon Nanotube-ZnO Nanosphere Heterostructures: Low-Temperature Chemical Reaction Synthesis, Photoluminescence, and Their Application for Room Temperature NH 3 Gas Sensor

Deren Yang

Papers

Electrically pumped ZnO film ultraviolet random lasers on silicon substrate

Room temperature electrically pumped ultraviolet random lasing from ZnO nanorod arrays on Si.

ZnO:Eu thin-films: Sol–gel derivation and strong photoluminescence from 5D0 → 7F0 transition of Eu3+ ions

Optical properties of sputtered hexagonal CdZnO films with band gap energies from 1.8 to 3.3 eV

Carbon Nanotube-ZnO Nanosphere Heterostructures: Low-Temperature Chemical Reaction Synthesis, Photoluminescence, and Their Application for Room Temperature NH 3 Gas Sensor