The optical properties of a high quality bulk $\mathrm{ZnO}$, thermally post treated in forming gas environment are investigated by temperature dependent continuous wave and time-resolved photoluminescence (PL) measurements. Several bound free exciton transitions along with their first excited states have been observed at low temperatures, the main neutral-donor-bound peak $3.3605\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ having linewidth $0.7\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ dominating...

Multiple quantum well (MQW) InGaN light emitting diodes with and without electron blocking layers, relatively small large barriers, p-type doping in the MQW region at ∼420nm were used to determine genesis of efficiency droop observed injection levels approximately ⩾50A∕cm2. Pulsed electroluminescence measurements, avoid heating effects, revealed that peak occurs ∼900A∕cm2 current density for Mg-doped barrier, near 550A∕cm2 lightly doped n-GaN layer, meant bring level closer holes, below...

Compared with conventional display technologies, liquid crystal (LCD), and organic light emitting diode (OLED), micro-LED displays possess potential advantages such as high contrast, fast response, relatively wide color gamut, low power consumption, long lifetime. Therefore, are deemed a promising technology that could replace LCD OLED at least in some applications. While the prospects bright, there still technological challenges have not yet been fully resolved order to realize volume...

Light emitting diodes (LEDs) based on InGaN suffer from efficiency droop at current injection levels as low 50 A cm−2. We investigated multiple quantum well LEDs with varying barrier thicknesses (3–12 nm) ∼400–410 nm to investigate the effect of hole mass and also find out possible solutions prevent droop. In electron blocking layers, when we reduced barriers 12 3 nm, density for peak or saturation external increased 200 1100 cm−2 under pulsed conditions, which eliminates heating effects a...

Indices of refraction for MgxZn1−xO epitaxial films grown by pulsed-laser deposition on sapphire substrates with x up to 0.36 were determined in the range wavelength 457–968 nm analysis optical transmission spectra and prism-coupled waveguide measurements. The dispersion follows first-order Sellmeier equation. Absorption coefficients, exciton energy gaps, binding energies alloys spectroscopy. excitonic absorption features clearly visible at room temperature despite alloy broadening. These...

This article discusses challenges in designing optically transparent antennas and filters for smart city applications. The concept seeks to alleviate urban that include infrastructure network capacity. proposed frequencies the next generation of wireless networks (5G) would result shorter broadcast distances dead zones. Additional access points signal repeaters embedded into existing infrastructure, by inserting windows via either meshed conductors or conductive oxides (TCOs), help mitigate...

High quality n-ZnO films on commercial p-type 6H–SiC substrates have been grown by plasma-assisted molecular-beam epitaxy, and n-ZnO∕p-SiC heterojunction mesa structures fabricated. Current-voltage characteristics of the had a very good rectifying diode-like behavior with leakage current less than 2×10−4A∕cm2 at −10V, breakdown voltage greater 20V, forward turn ∼5V, ∼2A∕cm2 8V. Photosensitivity diodes was studied room temperature photoresponsivity as high 0.045A∕W −7.5V reverse bias observed...

Light-emitting diodes (LEDs) have become quite a high-performance device of late and are revolutionizing the display illumination sectors our economy. Due to demands for better performance reduced energy consumption there is constant race towards converting every single electron hole pair in photons extracting them as well while using only minimum required voltage. This raises bar on GaN-based LEDs terms elimination nonradiative recombination processes not just at low but importantly if more...

High electron mobility was achieved in Al1−xInxN∕AlN∕GaN (x=0.20–0.12) heterostructure field effect transistors (HFETs) grown by metal-organic chemical vapor deposition. Reduction of In composition from 20% to 12% increased the room temperature equivalent two-dimensional-electron-gas density 0.90×1013to1.64×1013cm−2 with corresponding mobilities 1600 and 1410cm2∕Vs, respectively. The 10K reached 17600cm2∕Vs for nearly lattice-matched Al0.82In0.18N∕AlN∕GaN a sheet carrier 9.6×1012cm−2. For...

Ballistic and quasiballistic electron transport across the active InGaN layer are shown to be responsible for overflow electroluminescence efficiency droop at high current levels in light emitting diodes both experimentally by first-order calculations. An staircase injector with step-like increased In composition, an “electron cooler,” is proposed enhanced thermalization of injected hot electrons reduce mitigate droop. The experimental data show that results essentially same performance...

Low-cost, less-toxic, and abundantly-produced Ge1-xSnx alloys are an interesting class of narrow energy-gap semiconductors that received noteworthy interest in optical technologies. Incorporation α-Sn into Ge results indirect-to-direct bandgap crossover significantly improving light absorption emission relative to indirect-gap Ge. However, the energy-gaps reported for bulk have become a major impediment their widespread application optoelectronics. Herein, we report first colloidal synthesis...

The authors report the growth of semipolar (112¯2) GaN films on nominally on-axis (101¯0) m-plane sapphire substrates using metal organic chemical vapor deposition. High-resolution x-ray diffraction (XRD) results indicate a preferred orientation. Moreover, epitaxial lateral overgrowth (ELO) was carried out oriented templates. When ELO stripes were aligned along [112¯0]sapphire, Ga-polar wings inclined by 32° with respect to substrate plane smooth extended nonpolar a-plane surfaces and polar...

We perform a theoretical and experimental study of the optical properties $\mathrm{C}{\mathrm{H}}_{3}\mathrm{N}{\mathrm{H}}_{3}\mathrm{Pb}{\mathrm{I}}_{3}$ perovskite prepared by vapor-assisted solution process, motivated in part very high photovoltaic cell efficiencies. Several widespread approaches are used an attempt to determine most appropriate approach which would reproduce electronic structure perovskite. compare semilocal approximation density functional theory with hybrid...

In recent years, electrochemical biosensors based on semiconductor and metal nanostructures have attracted a great deal of attention as new instruments in the healthcare arsenal that could substantially enhance early diagnostics capabilities thus enable active health management. Among numerous materials studied, nanostructured ZnO has been recognized promising platform for biomedical applications owing to its low cost, relative ease preparation leading rich variety with high aspect ratios...

Dispersion of the ordinary and extraordinary indices refraction have been measured systematically for wurtzitic AlxGa1−xN epitaxial layers with 0.0⩽x⩽1.0 throughout visible wavelength region. The dispersion, by a prism coupling waveguide technique, is found to be well described Sellmeier relation. Discrepancies among previous measurements refractive index as consequence different growth conditions corresponding band gap bowing parameter, are reconciled when relation parameterized not x but energy.

We investigated the internal quantum efficiency (IQE) and relative external (EQE) of m-plane InGaN light emitting diodes (LEDs) grown on freestanding GaN at ∼400 nm for current densities up to 2500 A/cm2. IQE values extracted from intensity temperature dependent photoluminescence measurements were consistently higher, by some 30%, LEDs than reference c-plane having same structure, e.g., 80% versus 60% an injected steady-state carrier concentration 1.2×1018 cm−3. With increasing injection...

We overview recent progress in growth aspects of group III-nitride heterostructures for deep ultraviolet (DUV) light-emitting diodes (LEDs), with particular emphasis on the approaches attaining high-quality AlN and high Al-molar fraction AlGaN. The discussion commences introduction current status DUV LEDs remaining challenges. This segues into LED designs enabling device performance followed by review advances methods bulk single crystal intended as a native substrate together its UV...

Dispersion of the ordinary and extraordinary indices refraction for wurtzite AlxGa1−xN epitaxial layers with x=0.00, 0.04, 0.08, 0.11, 0.20 in range wavelengths 457<λ<980 nm were measured via a prism-coupled waveguide technique. The quantitative accuracy x is ±10% refractive ∼±0.01. dispersion found to be well described by 1st-order Sellmeier formula. A simple functional form presented that allows calculation as functions λ.

Significant improvement of structural and optical qualities GaN thin films on sapphire substrates was achieved by metal organic chemical vapor deposition with in situ SiNx nanonetwork. Transmission electron microscope (TEM) studies revealed that screw- edge-type dislocations were reduced to 4.4×107 1.7×107cm−2, respectively, for a ∼5.5-μm-thick layer. Furthermore, room temperature carrier lifetimes 2.22 2.49ns measured time-resolved photoluminescence (TRPL) samples containing single double...

For the last decade, optically transparent antennas have been a topic of research for applications ranging from satellite communication to window embedded telecommunications. The most common material used has so far Indium Tin Oxide (ITO). However, long term availability indium due worldwide shortages and increasing prices is great concern, necessitating exploration replacement materials. Among promising candidates zinc oxide heavily doped with gallium (GZO), which can be produced in form...

BexMgyZn1−x−yO semiconductor solid solutions are attractive for UV optoelectronics and electronic devices owing to their wide bandgap capability of lattice-matching ZnO. In this work, a combined experimental theoretical study lattice parameters, bandgaps, underlying properties, such as changes in band edge wavefunctions thin films, is carried out. Theoretical ab initio calculations predicting structural properties the whole compositional range materials compared with measurements from...

Ge1-xSnx alloy quantum dots (QDs) were synthesized with sizes ranging from 1-3 nm exhibiting visible orange-red photoluminescence. Composition dependent optical properties characterized and supported by theoretical calculations. Structural analysis suggests the QDs are diamond cubic phase, characteristic of thin films nanocrystals (NCs) reported to date.

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Y. Fu, T. Moon, F. Yun, Ü. Özgür, J. Q. Xie, S. Doğan, H. Morkoç, C. K. Inoki, Kuan, Lin Zhou, David Smith; Effectiveness of TiN porous templates on the reduction threading dislocations in GaN overgrowth by organometallic vapor-phase epitaxy. Appl. Phys. Lett. 24 January 2005; 86 (4): 043108....