A5019742720- GaN-based semiconductor devices and materials
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- Ga2O3 and related materials
- ZnO doping and properties
- Metal and Thin Film Mechanics
- Semiconductor Lasers and Optical Devices
- Silicon Carbide Semiconductor Technologies
- Chalcogenide Semiconductor Thin Films
- Photocathodes and Microchannel Plates
- Plasma Diagnostics and Applications
- Acoustic Wave Resonator Technologies
- Nanowire Synthesis and Applications
- Quantum Dots Synthesis And Properties
- Advanced Semiconductor Detectors and Materials
- Photonic and Optical Devices
- Semiconductor materials and interfaces
- Gas Sensing Nanomaterials and Sensors
- Optical Coatings and Gratings
- Anodic Oxide Films and Nanostructures
- Advanced Sensor and Energy Harvesting Materials
- Silicon Nanostructures and Photoluminescence
- Air Quality Monitoring and Forecasting
- Solid State Laser Technologies
- Advanced Chemical Physics Studies
Yale University
2015-2024
Xinyang Normal University
2024
Illinois State University
2021
Arizona State University
2021
University of New Haven
2020
University of Wisconsin–Madison
2015
Seoul Viosys (South Korea)
2014
Dankook University
2013
University of Florida
1997-2011
Jeonbuk National University
2011
Abstract Typical light‐emitting diodes (LEDs) have a form factor >(300 × 300) µm 2 . Such LEDs are commercially mature in illumination and ultralarge displays. However, recent LED research includes shrinking individual sizes from side lengths >300 to values <100 µm, leading devices called micro‐LEDs. Their advent creates number of exciting new application spaces. Here, review the principles applications micro‐LED technology is presented. In particular, implications reduced size...
Red-green-blue (RGB) full-color micro light-emitting diodes (μ-LEDs) fabricated from semipolar (20-21) wafers, with a quantum-dot photoresist color-conversion layer, were demonstrated. The InGaN/GaN μ-LEDs on large (4 in.) patterned sapphire substrates by orientation-controlled epitaxy. showed 3.2 nm peak wavelength shift and 14.7% efficiency droop under <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:mn>200</mml:mn> <mml:mtext> </mml:mtext>...
Abstract Micro light-emitting diode (micro-LED) will play an important role in the future generation of smart displays. They are found very attractive many applications, such as maskless lithography, biosensor, augmented reality (AR)/mixed etc, at same time. A monitor that can fulfill saturated color rendering, high display resolution, and fast response time is highly desirable, micro-LED-based technology could be our best chance to meet these requirements. At present, semiconductor-based...
We report on the growth and characterization of ultraviolet GaN quantum well light emitting diodes. The room-temperature electroluminescence emission was peaked at 353.6 nm with a narrow linewidth 5.8 nm. In simple planar devices, without any efforts to improve extraction efficiency, an output power 13 μW 20 mA measured, limited in present design by absorption cap layer buffer layer. Pulsed data demonstrate that does not saturate up current densities approaching 9 kA/cm2.
The evolution of stress in gallium nitride films on sapphire has been measured real time during metalorganic chemical vapor deposition. In spite the 16% compressive lattice mismatch GaN to sapphire, we find that consistently grows tension at 1050 °C. Furthermore, situ monitoring indicates there is no measurable relaxation tensile growth annealing or thermal cycling.
We describe a low-resistance quasi-ohmic contact to p-ZnSe which involves the injection of holes from heavily doped ZnTe into ZnSe via Zn(Se,Te) pseudograded band gap region. The specific resistance is measured be in range 2–8×10−3 Ω cm2. graded heterostructure scheme incorporated as an efficient injector for laser diode and light emitting devices, demonstrating usefulness this new at actual device current densities.
A porous medium is a special type of material where voids are created in solid medium. The introduction pores into bulk can profoundly affect its physical properties and enable interesting mechanisms. In this paper, we report the use mesoporous GaN to address long-standing challenge devices: tuning optical index epitaxial structures without compromising structural electrical properties. By controlling doping electrochemical etching bias, able control pore morphology from macro- meso-...
A vertical-cavity surface-emitting perovskite laser is achieved using a microcavity configuration where CH3 NH3 PbI3 thin solid films are embedded within custom GaN-based high-quality (Q-factor) resonator. This single-mode reaches low threshold (≈7.6 µJ cm-2 ) at room temperature and emits spatially coherent Gaussian beams. The devices allow direct access to the study of gain dynamics material robustness.
We report the use of hydrofluoric acid (HF) as an electrolyte in etching and porosifying GaN. HF is found to be effective rendering a wide range nanoporous morphology, from curved branches highly parallel straight pores. Under suitable conditions, porosification proceeds at rate greater than 100 μm/min. To elucidate mechanism, cyclic voltammetry performed, together with parametric mapping electrolysis variables such doping GaN, concentration electrolyte, anodization voltage. demonstrate that...
The light-emitting diode (LED) is among promising candidates of light sources in visible communication (VLC); however, strong internal polarization fields common c-plane LEDs, especially green result low frequency and limited transmission performance. This study aims to overcome the 3-dB bandwidth long-wavelength InGaN/GaN LEDs. Thus, semipolar (20–21) micro-LEDs (μLEDs) were fabricated through several improved approaches on epitaxy chip processes. μLED exhibits a 525 nm peak wavelength good...
The band gap of AlxGa1−xN is measured for the composition range 0⩽x&lt;0.45; resulting bowing parameter, b=+0.69 eV, compared to 20 previous works. A correlation found between gaps and methods used epitaxial growth AlxGa1−xN: directly nucleated or buffered growths initiated on sapphire at temperatures T&gt;800 °C usually lead stronger apparent (b&gt;+1.3 eV); while using low-temperature buffers sapphire, followed by high-temperature growth, weaker (b&lt;+1.3 eV). Extant data...
Unpassivated AlGaN/GaN high-electron-mobility transistors show significant gate lag effects due to the presence of surface states in region between and drain contact. Low-temperature (100 °C) layers MgO or Sc2O3 deposited by plasma-assisted molecular-beam epitaxy are shown effectively mitigate collapse current through passivation traps. These dielectrics may have advantages over more conventional SiNX terms long-term device stability.
The density of threading dislocations (TD) in GaN grown directly on flat sapphire substrates is typically greater than 109/cm2. can be decreased by orders magnitude using cantilever epitaxy, which employs pre-patterned to provide reduced-dimension mesa regions for nucleation and etched trenches between them suspended lateral growth or AlGaN. substrate with narrow lines a depth that permits coalescence laterally growing III–N nucleated the surfaces before vertical fills trench....
In situ optical reflectance transients reveal that the morphology evolution of initial low-temperature buffer layer strongly influences structural and electrical quality high-temperature GaN films. Moreover, layer, specifically spatial orientational distributions nuclei, is affected by H2. The growth conditions for which surface smoothness maintained throughout two-step do not necessarily produce best final films; instead, there may be an optimal roughness incubation period en route to
In situ stress monitoring has been employed during metalorganic chemical vapor deposition of AlGaN/GaN distributed Bragg reflectors (DBRs). It was found that the insertion multiple AlN interlayers is effective in converting tensile growth typically observed this system into compression, thus alleviating problem crack generation. Crack-free a 60 pair Al0.20Ga0.80N/GaN quarter-wavelength DBR obtained over entire 2 in. wafer; an accompanying reflectivity at least 99% near peak wavelength around 380 nm.
In organometallic vapor phase epitaxial growth of GaN on sapphire, the role low-temperature-deposited interlayers inserted between high-temperature-grown layers was investigated by in situ stress measurement, X-ray diffraction, and transmission electron microscopy. Insertion a series low temperature reduces density threading dislocations while simultaneously increasing tensile during growth, ultimately resulting cracking film. Low AlN were found to be effective suppressing reducing stress....
Continuous-wave (CW) operation of ridge waveguide quantum well diode lasers in the green/blue has been demonstrated at voltages as low 4.4V ZnCdSe/ZnSSe/ZnMgSSe pseudomorphic separate confinement heterostructures, with output powers up to 10mW.
The microstructure of a degraded II-VI blue-green laser diode based on the ZnCdSe/ZnSSe/ ZnMgSSe pseudomorphic separate confinement heterostructure has been examined by transmission electron microscopy. Triangular nonluminescent dark defects observed in stripe region electroluminescence microscopy have identified to be dislocation networks developed at quantum-well region. nucleated threading dislocations originating from pairs V-shaped stacking faults which are or near II-VI/GaAs interface...
Epilayers of the previously hypothetical zinc-blende MnTe have been grown by molecular beam epitaxy. Epitaxial layers (0.5 μm thick) were characterized using x-ray diffraction and transmission electron microscopy; optical reflectance measurements indicate a band gap ∼3.2 eV. A series strained single quantum well structures was fabricated with forming barrier to CdTe regions; photoluminescence spectra transitions corresponding strong hole confinement.
In this paper we provide explanations to the complex growth phenomena of GaN heteroepitaxy on nonpolar orientations using concept kinetic Wulff plots (or v-plots). Quantitative mapping in polar, semipolar, and angles are achieved a differential measurement technique from selective area growth. An accurate knowledge topography serves as an important stepping stone toward model-based control Examples illustrated correlate dynamics based with commonly observed features, including anisotropic...
This work represents a comprehensive attempt to correlate the heteroepitaxial dynamics in experiments with fundamental principles crystal growth using kinetic Wulff plot (or v-plot). Selective area is employed monitor advances of convex and concave facets toward construction v-plot as guidepost for GaN heteroepitaxy. A procedure developed apply experimentally determined plots interpretation design evolution nucleation island coalescence. offers cohesive rational model heteroepitaxy on polar,...