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Monolithic Broadband InGaN Light-Emitting Diode

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Monolithic Broadband InGaN Light-Emitting Diode by Cong Feng, Jian-An Huang, Hoi Wai Choi.

A monolithic nonphosphor broadband-emission light-emitting diode is demonstrated, comprising a combination of high-density microstructured and nanostructured InGaN-GaN quantum wells fabricated using top-down approach. Broadband emission achieved by taking advantage low-dimensional-induced strain-relaxation highly strained wells, combining light emitted from strain-relaxed nanotips at wavelengths shorter than the as-grown as much 80 nm with longer-wavelength larger nonrelaxed microdisks. The localized characteristics have been studied spatially resolved near-field photoluminescence spectroscopy which enabled both intensity spectrum individual to be distinguished larger-dimensioned regions. Distinctive blue-green-yellow can observed electroluminescent device, whose continuous broadband characterized CIE coordinates (0.39, 0.47) color rendering in…

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The role of surface diffusion and wing tilt in the formation of localized stacking faults in high In-content InGaN MQW nanostructures

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The role of surface diffusion and wing tilt in the formation of localized stacking faults in high In-content InGaN MQW nanostructures by Yoshitake Nakajima, P. Daniel Dapkus.

Yellow and green emitting multiple quantum well structures are grown on nanostripe templates with {10-11} facets. SEM cathodoluminescence measurements show a correlation between rough surface morphology near the bottom of stripes non-radiative recombination centers. Transmission electron microscopy (TEM) analysis shows that these instabilities result stacking faults generated from (QW) regions pyramid propagate to surface. HRTEM images I1 type which is formed by removal one half basal plane relieve compressive strain in InGaN QW. Thicker QWs as growth rate enhancement due diffusion precursors mask cause increased strain. Additionally, induced bending nanostructure towards further increases experienced QW thereby causing localized defect gener…

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Optical properties of III-nitride laser diodes with wide InGaN quantum wells

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Optical properties of III-nitride laser diodes with wide InGaN quantum wells by Grzegorz Muziol, Mateusz Hajdel, Czeslaw Skierbiszewski, Marcin Siekacz, K. Szkudlarek, Szymon Stanczyk, Henryk Turski.

In this paper we show that, despite a high piezoelectric field, wide InGaN quantum well (QW) can be more effective as the active region of laser diodes (LDs) than thin ones usually used. The optical gain in LDs with single QW is studied. It shown that differential LD 10.4?nm higher three 2.6?nm thick QWs. interpreted originating from transitions through excited states. Additionally, substantial difference lasing spectra between and QWs found.

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Phosphor-converted white light from blue-emitting InGaN microrod LEDs

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Phosphor-converted white light from blue-emitting InGaN microrod LEDs by Tilman Schimpke, Martin Mandl, Ion Stoll, Bianca Pohl-Klein, Daniel Bichler, Franz Zwaschka, Johanna Strube-Knyrim, Barbara Huckenbeck, Benjamin Max, Marcus Müller, Peter Veit, Frank Bertram, Jürgen Christen, Jana Hartmann, Andreas Waag, Hans-Juergen Lugauer, Martin Strassburg.

A uniform array of gallium nitride core-shell microrod (MR) light-emitting diode (LED) structures was grown by metalorganic vapor phase epitaxy. Defects and the quantum well (QW) luminescence in an individual rod were investigated scanning tunneling electron microscopy (STEM) STEM cathodoluminescence. Luminescence with different wavelength detected from wells on semipolar tip facets nonpolar sidewalls MRs. Furthermore, MR is processed into LED chips. The electro-optical characteristics devices are analyzed. Two separate emission bands distinguished, which attributed to QWs sidewalls, respectively. To obtain white LEDs, micrograin phosphors developed fit between By using electrophoretic particle deposition, these deposited onto Color coordinates, color temperature, device efficiency evaluated.

Blue (top) phosphor-converted (bottom) LEDs 4″ wafer.

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Pros and cons of green InGaN laser on c-plane GaN

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Pros and cons of green InGaN laser on c-plane GaN by Uwe Strauß, Adrian Stefan Avramescu, Teresa Lermer, Désirée Queren, Alvaro Gomez-Iglesias, Christoph Eichler, Jens Müller, Georg Brüderl, Stephan Lutgen.

The challenges of green InGaN lasers are discussed concerning material quality as a function composition, quantum well design and piezoelectrical fields. Investigations polar designs comparison with simulated non-polar structures demonstrate that the indium rich layers is more important than influence interface charges. A high risk dark spots at In concentrations 26–33% observed. Small changes about 2% significant reduce or increase quantity size luminescence areas. Polar trade-off between low 4 nm wide wells overlap electrons holes in 2 nm narrow designs. Furthermore, our single have less non-radiative defects multi-quantum structures. Optimized active layer qualities enable us to get on c-plane substrates for cw operation 515–524 nm wall plug efficiencies 3.9–2.3%. Slope efficiency 0.3–0.4 W/A allows up now highest optical output power 50 mW.

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Hybrid functional investigations of band gaps and band alignments for AlN, GaN, InN, and InGaN

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Hybrid functional investigations of band gaps and band alignments for AlN, GaN, InN, and InGaN by Poul Georg Moses, Maosheng Miao, Qimin Yan, Chris G. Van de Walle.

Band gaps and band alignments for AlN, GaN, InN, InGaN alloys are investigated using density functional theory with the Heyd-Scuseria-Ernzerhof {HSE06 [J. Heyd, G. E. Scuseria, M. Ernzerhof, J. Chem. Phys. 134, 8207 (2003); 124, 219906 (2006)]} XC functional. The gap of as a function In content is calculated strong bowing at low found, described by parameters 2.29 eV 6.25% 1.79 12.5%, indicating cannot be single composition-independent parameter. Valence-band maxima (VBM) conduction-band minima (CBM) aligned combining bulk calculations surface nonpolar surfaces. influence termination [(1100) m-plane or (1120) a-plane] thoroughly investigated. We find that relaxed surfaces binary nitrides difference in electron affinities between m- a-plane less than 0.1 eV. absolute found to strongly depend on choice However, we relative sensitive particular, may based Perdew-Becke-Ernzerhof P. Perdew, K. Burke, Rev. Lett. 3865 (1996)] HSE06 lattice parameters. For VBM linear majority band-gap located CBM. Based predict will suited water splitting up 50% content.

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Vertical profiling of ultrafast carrier dynamics in partially strain relaxed and strained InGaN grown on GaN/sapphire template of different In composition

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Vertical profiling of ultrafast carrier dynamics in partially strain relaxed and strained InGaN grown on GaN/sapphire template of different In composition by Kwangwook Park, Jung-Wook Min, Sergei Lopatin, Bambar Davaasuren, Tae-Yong Park, S. Boon Ooi, Hyeongmun Kim, Sang-Youp Yim, Gyeong Cheol Park, Chul Kang.

• InGaN is an important alloy of having viable bandgap energy by changing In content. Partially relaxed samples different compositions were grown using PAMBE. Vertical profiling ultrafast carrier dynamics performed OPTP. Fast decay caused hot cooling due to uniformly distributed oxygen. Slow localization V-defect at InGaN/GaN interface. one the ternary alloys which enables nitrides have in a wide range 0.77-3.44 eV corresponding photon wavelength 360-1610 nm simply adjusting However, research on has primarily focused low-dimensional structures though knowledge physical properties bulk thin-film designing optoelectronic applications that utilize thick layers. this study, we revisited partially strain layers compositions. We found fast was presence oxygen impurity, and slow governed initiated V-defects concentrated bottom layer starting also observed became severe, lifetime decreased as composition within increased. Our observation gives guidance layers, such buffer for long-wavelength light emitting diodes well solar absorber photovoltaic cells.

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Enhancement in hole-injection efficiency of blue InGaN light-emitting diodes from reduced polarization by some specific designs for the electron blocking layer

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Enhancement in hole-injection efficiency of blue InGaN light-emitting diodes from reduced polarization by some specific designs for the electron blocking layer by Yen-Kuang Kuo, Jih-Yuan Chang, Miao-Chan Tsai.

Some specific designs on the electron blocking layer (EBL) of blue InGaN LEDs are investigated numerically in order to improve hole injection efficiency without losing capability electrons. Simulation results show that polarization-induced downward band bending is mitigated these redesigned EBLs and, hence, increases markedly. The optical performance and droop also improved, especially under situation high current injection.

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Effects of Built-In Polarization and Carrier Overflow on InGaN Quantum-Well Lasers With Electronic Blocking Layers

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Effects of Built-In Polarization and Carrier Overflow on InGaN Quantum-Well Lasers With Electronic Blocking Layers by Jun-Rong Chen, Chung-Hsien Lee, Tsung-Shine Ko, Yi-An Chang, Tien-Chang Lu, Hao-Chung Kuo, Yen-Kuang Kuo, Shing-Chung Wang.

Effects of built-in polarization and carrier overflow on InGaN quantum-well lasers with a ternary AlGaN or quaternary AlInGaN electronic blocking layer (EBL) have been numerically investigated by employing an advanced device-simulation program. The simulation results indicate that the characteristics can be improved using EBL. When aluminum indium compositions in EBL are appropriately designed, charge density at interface between barrier reduced. Under this circumstance, electron leakage current laser threshold obviously decreased as compared structure conventional when is taken into account calculation. Furthermore, also gives higher refractive index than EBL, which benefit for optical confinement factor operations.

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Rate equation analysis of efficiency droop in InGaN light-emitting diodes

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Rate equation analysis of efficiency droop in InGaN light-emitting diodes by Han-Youl Ryu, Hyunsung Kim, Jongin Shim.

Efficiency droop in InGaN light-emitting diodes (LEDs) is analyzed based on the rate equation model. By using peak point of efficiency versus current-density relation as parameters analysis, internal quantum and each recombination current at arbitrary density can be unambiguously determined without any knowledge A, B, C coefficients. The theoretical analysis compared with measured a LED sample good agreement between model experiment found. investigation coefficients shows that Auger alone not sufficient to explain LEDs.

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