The Experts below are selected from a list of 1440 Experts worldwide ranked by ideXlab platform
James S Speck - One of the best experts on this subject based on the ideXlab platform.
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room temperature continuous wave electrically driven Semipolar 2021 blue laser diodes heteroepitaxially grown on a sapphire substrate
ACS Photonics, 2020Co-Authors: Haojun Zhang, James S Speck, Shuji Nakamura, Jie Song, Steven P. DenbaarsAbstract:Growth of Semipolar GaN laser diodes (LDs) on low-cost and large-size foreign substrates is crucial yet remains very challenging. In this study, we report the world’s first continuous-wave (CW) ele...
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560 nm ingan micro leds on low defect density and scalable 20 21 Semipolar gan on patterned sapphire substrates
Optics Express, 2020Co-Authors: Michel Khoury, Shuji Nakamura, James S Speck, Jie Song, Haojun Zhang, Bastien Bonef, Tom Mates, Matthew S Wong, Joown Choi, Steven P. DenbaarsAbstract:We demonstrate InGaN-based Semipolar 560 nm micro-light-emitting diodes with 2.5% EQE on high-quality and low-defect-density (20-21) GaN templates grown on scalable and low-cost sapphire substrates. Through transmission electron microscopy observations, we discuss how the management of misfit dislocations and their confinement in areas away from the active light-emitting region is necessary for improving device performance. We also discuss how the patterning of Semipolar GaN on sapphire influences material properties in terms of surface roughness and undesired faceting in addition to indium segregation at the proximity of defected areas.
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efficient Semipolar 11 22 550 nm yellow green ingan light emitting diodes on low defect density 11 22 gan sapphire templates
ACS Applied Materials & Interfaces, 2017Co-Authors: Hongjian Li, Shuji Nakamura, Philippe De Mierry, Michel Khoury, Bastien Bonef, Abdullah I Alhassan, Asad J Mughal, Ezzah Azimah, M E A Samsudin, James S SpeckAbstract:We demonstrate efficient Semipolar (11–22) 550 nm yellow/green InGaN light-emitting diodes (LEDs) with In0.03Ga0.97N barriers on low defect density (11–22) GaN/patterned sapphire templates. The In0.03Ga0.97N barriers were clearly identified, and no InGaN clusters were observed by atom probe tomography measurements. The Semipolar (11–22) 550 nm InGaN LEDs (0.1 mm2 size) show an output power of 2.4 mW at 100 mA and a peak external quantum efficiency of 1.3% with a low efficiency drop. In addition, the LEDs exhibit a small blue-shift of only 11 nm as injection current increases from 5 to 100 mA. These results suggest the potential to produce high efficiency Semipolar InGaN LEDs with long emission wavelength on large-area sapphire substrates with economical feasibility.
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Efficient Semipolar (11–22) 550 nm Yellow/Green InGaN Light-Emitting Diodes on Low Defect Density (11–22) GaN/Sapphire Templates
2017Co-Authors: Michel Khoury, Shuji Nakamura, Philippe De Mierry, Bastien Bonef, Abdullah I Alhassan, Asad J Mughal, Ezzah Azimah, M E A Samsudin, James S SpeckAbstract:We demonstrate efficient Semipolar (11–22) 550 nm yellow/green InGaN light-emitting diodes (LEDs) with In0.03Ga0.97N barriers on low defect density (11–22) GaN/patterned sapphire templates. The In0.03Ga0.97N barriers were clearly identified, and no InGaN clusters were observed by atom probe tomography measurements. The Semipolar (11–22) 550 nm InGaN LEDs (0.1 mm2 size) show an output power of 2.4 mW at 100 mA and a peak external quantum efficiency of 1.3% with a low efficiency drop. In addition, the LEDs exhibit a small blue-shift of only 11 nm as injection current increases from 5 to 100 mA. These results suggest the potential to produce high efficiency Semipolar InGaN LEDs with long emission wavelength on large-area sapphire substrates with economical feasibility
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ghz modulation enabled using large extinction ratio waveguide modulator integrated with 404 nm gan laser diode
IEEE Photonics Conference, 2016Co-Authors: Chao She, Steven P. Denbaars, Changmi Lee, Shuji Nakamura, Ahmed Y Alyamani, Muni M Eldesouki, James S Speck, Oo S OoiAbstract:A 404-nm emitting InGaN-based laser diode with integrated-waveguide-modulator showing a large extinction ratio of 11.3 dB was demonstrated on Semipolar (2021) plane GaN substrate. The device shows a low modulation voltage of −2.5 V and ∼ GHz −3 dB bandwidth, enabling 1.7 Gbps data transmission.
Shuji Nakamura - One of the best experts on this subject based on the ideXlab platform.
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toward heteroepitaxially grown Semipolar gan laser diodes under electrically injected continuous wave mode from materials to lasers
Applied physics reviews, 2020Co-Authors: Haojun Zhang, Jie Song, Shuji Nakamura, Steven P. DenbaarsAbstract:III-nitrides based light-emitting diodes and laser diodes (LDs) have shown great success as solid-state lighting sources, but the development of common c-plane (0001) polar GaN emitters is facing limitations due to quantum-confinement Stark effect, efficiency drop, low efficiency at green range, and peak wavelength blue-shift. Efficient Semipolar or nonpolar GaN light emitting diodes and LDs have been successfully demonstrated by growing on Semipolar or nonpolar free-standing GaN substrates. The small size and high cost of high crystal quality Semipolar or nonpolar free-standing GaN substrates, which are sliced from hydride vapor phase epitaxy grown c-plane bulk GaN substrate, have severely limited their commercial development and application. Achieving scalable heteroepitaxial Semipolar GaN materials with a very low density of basal-stacking faults (BSFs) on a foreign substrate remains very challenging. The recent breakthrough in the demonstration of continuous-wave (CW) Semipolar (20 2 ¯1) LDs at room-temperature on Semipolar GaN/sapphire template marks a milestone in exploring high crystal quality heteroepitaxial Semipolar GaN materials and low-cost Semipolar emitters. Here, we review the key progress through the past years about the development of heteroepitaxial Semipolar GaN materials including epitaxial lateral overgrowth, orientation controlling epitaxy, BSFs burying by neighboring Ga-polar (0001) GaN with air voids, facet-engineering orientation control epitaxy, resulting in a low density or free of basal stacking faults. Furthermore, we discuss the heteroepitaxially grown pulsed Semipolar (11 2 ¯2) blue LDs and CW Semipolar (20 2 ¯1) LDs.
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high polarization and fast modulation speed of dual wavelengths electroluminescence from Semipolar 20 21 micro light emitting diodes with indium tin oxide surface grating
Applied Physics Letters, 2020Co-Authors: Haojun Zhang, Jie Song, Shuji Nakamura, Steven P. DenbaarsAbstract:We present highly polarized dual wavelength Semipolar InGaN micro-light-emitting diodes (μLEDs) by combining an indium tin oxide (ITO) surface grating and Al-coated dual-color surface plasmons (DSPs). The ITO grating DSPs enable a significant enhancement of the polarization ratio (PR) from electrically driven Semipolar (20-21) μLEDs with dual emission wavelengths: the overall PR was increased by 1.7-folds and the output power was enhanced by 78% as compared to the conventional Semipolar μLEDs at an injection current density of 100 A/cm2. Moreover, a high 3 dB modulation bandwidth of 612 MHz is achieved at ∼1.4 kA/cm2 in a visible-light communication (VLC) system, suggesting a near 1.24 Gbit/s under a non-return-to-zero on-off keying modulation scheme. This design marks significant progress in developing polarized μLEDs with potential applications in various fields, such as displays and VLC.
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room temperature continuous wave electrically driven Semipolar 2021 blue laser diodes heteroepitaxially grown on a sapphire substrate
ACS Photonics, 2020Co-Authors: Haojun Zhang, James S Speck, Shuji Nakamura, Jie Song, Steven P. DenbaarsAbstract:Growth of Semipolar GaN laser diodes (LDs) on low-cost and large-size foreign substrates is crucial yet remains very challenging. In this study, we report the world’s first continuous-wave (CW) ele...
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560 nm ingan micro leds on low defect density and scalable 20 21 Semipolar gan on patterned sapphire substrates
Optics Express, 2020Co-Authors: Michel Khoury, Shuji Nakamura, James S Speck, Jie Song, Haojun Zhang, Bastien Bonef, Tom Mates, Matthew S Wong, Joown Choi, Steven P. DenbaarsAbstract:We demonstrate InGaN-based Semipolar 560 nm micro-light-emitting diodes with 2.5% EQE on high-quality and low-defect-density (20-21) GaN templates grown on scalable and low-cost sapphire substrates. Through transmission electron microscopy observations, we discuss how the management of misfit dislocations and their confinement in areas away from the active light-emitting region is necessary for improving device performance. We also discuss how the patterning of Semipolar GaN on sapphire influences material properties in terms of surface roughness and undesired faceting in addition to indium segregation at the proximity of defected areas.
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enhancement of n type gan 20 21 Semipolar surface morphology in photo electrochemical undercut etching
Applied Physics Express, 2019Co-Authors: Arwa Saud Abbas, Shuji Nakamura, Ahmed Y Alyamani, Steven P DembaarsAbstract:An ice bath photo-electrochemical (PEC) undercut etching technique to separate devices from substrates is described. Smoothly etched Si-doped () GaN is produced by etching a 40 nm relaxed sacrificial layer single quantum well. This has potential for improving the active region quality of Semipolar green-emitter. Removal of unetched misfit dislocations revealed an RMS surface roughness decreasing from σ rms = 5.136 to 0.25 nm. In view of the development of green-light emitters, the interplay between the effects of reactant diffusion-limited etch process and defect-selective etching is demonstrated by enhancing PEC etching performance toward a smooth n-type Semipolar GaN surface.
Steven P. Denbaars - One of the best experts on this subject based on the ideXlab platform.
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toward heteroepitaxially grown Semipolar gan laser diodes under electrically injected continuous wave mode from materials to lasers
Applied physics reviews, 2020Co-Authors: Haojun Zhang, Jie Song, Shuji Nakamura, Steven P. DenbaarsAbstract:III-nitrides based light-emitting diodes and laser diodes (LDs) have shown great success as solid-state lighting sources, but the development of common c-plane (0001) polar GaN emitters is facing limitations due to quantum-confinement Stark effect, efficiency drop, low efficiency at green range, and peak wavelength blue-shift. Efficient Semipolar or nonpolar GaN light emitting diodes and LDs have been successfully demonstrated by growing on Semipolar or nonpolar free-standing GaN substrates. The small size and high cost of high crystal quality Semipolar or nonpolar free-standing GaN substrates, which are sliced from hydride vapor phase epitaxy grown c-plane bulk GaN substrate, have severely limited their commercial development and application. Achieving scalable heteroepitaxial Semipolar GaN materials with a very low density of basal-stacking faults (BSFs) on a foreign substrate remains very challenging. The recent breakthrough in the demonstration of continuous-wave (CW) Semipolar (20 2 ¯1) LDs at room-temperature on Semipolar GaN/sapphire template marks a milestone in exploring high crystal quality heteroepitaxial Semipolar GaN materials and low-cost Semipolar emitters. Here, we review the key progress through the past years about the development of heteroepitaxial Semipolar GaN materials including epitaxial lateral overgrowth, orientation controlling epitaxy, BSFs burying by neighboring Ga-polar (0001) GaN with air voids, facet-engineering orientation control epitaxy, resulting in a low density or free of basal stacking faults. Furthermore, we discuss the heteroepitaxially grown pulsed Semipolar (11 2 ¯2) blue LDs and CW Semipolar (20 2 ¯1) LDs.
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high polarization and fast modulation speed of dual wavelengths electroluminescence from Semipolar 20 21 micro light emitting diodes with indium tin oxide surface grating
Applied Physics Letters, 2020Co-Authors: Haojun Zhang, Jie Song, Shuji Nakamura, Steven P. DenbaarsAbstract:We present highly polarized dual wavelength Semipolar InGaN micro-light-emitting diodes (μLEDs) by combining an indium tin oxide (ITO) surface grating and Al-coated dual-color surface plasmons (DSPs). The ITO grating DSPs enable a significant enhancement of the polarization ratio (PR) from electrically driven Semipolar (20-21) μLEDs with dual emission wavelengths: the overall PR was increased by 1.7-folds and the output power was enhanced by 78% as compared to the conventional Semipolar μLEDs at an injection current density of 100 A/cm2. Moreover, a high 3 dB modulation bandwidth of 612 MHz is achieved at ∼1.4 kA/cm2 in a visible-light communication (VLC) system, suggesting a near 1.24 Gbit/s under a non-return-to-zero on-off keying modulation scheme. This design marks significant progress in developing polarized μLEDs with potential applications in various fields, such as displays and VLC.
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room temperature continuous wave electrically driven Semipolar 2021 blue laser diodes heteroepitaxially grown on a sapphire substrate
ACS Photonics, 2020Co-Authors: Haojun Zhang, James S Speck, Shuji Nakamura, Jie Song, Steven P. DenbaarsAbstract:Growth of Semipolar GaN laser diodes (LDs) on low-cost and large-size foreign substrates is crucial yet remains very challenging. In this study, we report the world’s first continuous-wave (CW) ele...
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560 nm ingan micro leds on low defect density and scalable 20 21 Semipolar gan on patterned sapphire substrates
Optics Express, 2020Co-Authors: Michel Khoury, Shuji Nakamura, James S Speck, Jie Song, Haojun Zhang, Bastien Bonef, Tom Mates, Matthew S Wong, Joown Choi, Steven P. DenbaarsAbstract:We demonstrate InGaN-based Semipolar 560 nm micro-light-emitting diodes with 2.5% EQE on high-quality and low-defect-density (20-21) GaN templates grown on scalable and low-cost sapphire substrates. Through transmission electron microscopy observations, we discuss how the management of misfit dislocations and their confinement in areas away from the active light-emitting region is necessary for improving device performance. We also discuss how the patterning of Semipolar GaN on sapphire influences material properties in terms of surface roughness and undesired faceting in addition to indium segregation at the proximity of defected areas.
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impact of crystal orientation on the modulation bandwidth of ingan gan light emitting diodes
Applied Physics Letters, 2018Co-Authors: Morteza Monavarian, Steven P. Denbaars, Ashwin K. Rishinaramangalam, Arman Rashidi, Andrew Aragon, Daniel F FeezellAbstract:High-speed InGaN/GaN blue light-emitting diodes (LEDs) are needed for future gigabit-per-second visible-light communication systems. Large LED modulation bandwidths are typically achieved at high current densities, with reports close to 1 GHz bandwidth at current densities ranging from 5 to 10 kA/cm2. However, the internal quantum efficiency (IQE) of InGaN/GaN LEDs is quite low at high current densities due to the well-known efficiency droop phenomenon. Here, we show experimentally that nonpolar and Semipolar orientations of GaN enable higher modulation bandwidths at low current densities where the IQE is expected to be higher and power dissipation is lower. We experimentally compare the modulation bandwidth vs. current density for LEDs on nonpolar (101¯0), Semipolar (202¯1¯), and polar 0001 orientations. In agreement with wavefunction overlap considerations, the experimental results indicate a higher modulation bandwidth for the nonpolar and Semipolar LEDs, especially at relatively low current densities....
Daniel F Feezell - One of the best experts on this subject based on the ideXlab platform.
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impact of crystal orientation on the modulation bandwidth of ingan gan light emitting diodes
Applied Physics Letters, 2018Co-Authors: Morteza Monavarian, Steven P. Denbaars, Ashwin K. Rishinaramangalam, Arman Rashidi, Andrew Aragon, Daniel F FeezellAbstract:High-speed InGaN/GaN blue light-emitting diodes (LEDs) are needed for future gigabit-per-second visible-light communication systems. Large LED modulation bandwidths are typically achieved at high current densities, with reports close to 1 GHz bandwidth at current densities ranging from 5 to 10 kA/cm2. However, the internal quantum efficiency (IQE) of InGaN/GaN LEDs is quite low at high current densities due to the well-known efficiency droop phenomenon. Here, we show experimentally that nonpolar and Semipolar orientations of GaN enable higher modulation bandwidths at low current densities where the IQE is expected to be higher and power dissipation is lower. We experimentally compare the modulation bandwidth vs. current density for LEDs on nonpolar (101¯0), Semipolar (202¯1¯), and polar 0001 orientations. In agreement with wavefunction overlap considerations, the experimental results indicate a higher modulation bandwidth for the nonpolar and Semipolar LEDs, especially at relatively low current densities....
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internal quantum efficiency and carrier dynamics in Semipolar 20 21 ingan gan light emitting diodes
Optics Express, 2017Co-Authors: S Okur, Ashwin K. Rishinaramangalam, Mohsen Nami, Sang H Oh, S P Denbaars, Igal Brener, Daniel F FeezellAbstract:The internal quantum efficiencies (IQE) and carrier lifetimes of Semipolar (202¯1¯) InGaN/GaN LEDs with different active regions are measured using temperature-dependent, carrier-density-dependent, and time-resolved photoluminescence. Three active regions are investigated: one 12-nm-thick single quantum well (SQW), two 6-nm-thick QWs, and three 4-nm-thick QWs. The IQE is highest for the 12-nm-thick SQW and decreases as the well width decreases. The radiative lifetimes are similar for all structures, while the nonradiative lifetimes decrease as the well width decreases. The superior IQE and longer nonradiative lifetime of the SQW structure suggests using thick SQW active regions for high brightness Semipolar (202¯1¯) LEDs.
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Semipolar ingan gan nanostructure light emitting diodes on c plane sapphire
Applied Physics Express, 2016Co-Authors: Ashwin K. Rishinaramangalam, Mohsen Nami, Michael N Fairchild, Darryl M Shima, Ganesh Balakrishnan, S R J Brueck, Daniel F FeezellAbstract:The fabrication of electrically injected triangular-nanostripe core–shell Semipolar III–nitride LEDs (TLEDs) is demonstrated using interferometric lithography and catalyst-free bottom-up selective-area metal–organic chemical vapor deposition (MOCVD). This alternative approach enables Semipolar orientations on inexpensive, c-plane sapphire substrates, in comparison with planar growth on free-standing GaN substrates. Transmission electron microscopy and energy dispersive X-ray spectroscopy reveal nonuniform quantum well thickness and composition, respectively, as a function of location on the triangular stripes. The broad electroluminescence spectra, wavelength shift with increasing current density, and nonlinear light vs current characteristics are well correlated with the observed quantum-well nonuniformities.
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Semipolar hbox 20 bar hbox 2 bar hbox 1 ingan gan light emitting diodes for high efficiency solid state lighting
IEEE\ OSA Journal of Display Technology, 2013Co-Authors: Daniel F Feezell, Steven P. Denbaars, James S Speck, Shuji NakamuraAbstract:This work examines the effects of polarization-related electric fields on the energy band diagrams, wavelength shift, wave function overlap, and efficiency droop for InGaN quantum wells on various crystal orientations, including polar (0001) (c -plane), Semipolar (2021), Semipolar (2021), and nonpolar (1010) (m-plane). Based on simulations, we show that the Semipolar (2021) orientation exhibits excellent potential for the development of high-efficiency, low-droop light-emitting diodes (LEDs). We then present recent advancements in crystal growth, optical performance, and thermal performance of Semipolar (2021) LEDs. Finally, we demonstrate a low-droop, high-efficiency single-quantum-well blue Semipolar (2021) LED with an external quantum efficiency of more than 50% at 100 A/cm2.
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development of gallium nitride based light emitting diodes leds and laser diodes for energy efficient lighting and displays
Acta Materialia, 2013Co-Authors: Steven P. Denbaars, Yuji Zhao, Shinichi Tanaka, Robert M Farrell, Daniel F Feezell, Katheryn Kelchner, Siddha Pimputkar, Nathan Pfaff, Stacia Keller, U K MishraAbstract:Abstract Light-emitting diodes (LEDs) fabricated from gallium nitride (GaN) have led to the realization of high-efficiency white solid-state lighting. Currently, GaN white LEDs exhibit luminous efficacy greater than 150 lm W −1 , and external quantum efficiencies higher than 60%. This has enabled LEDs to compete with traditional lighting technologies, such as incandescent and compact fluorescent (CFL) lighting. Further improvements in materials quality and cost reduction are necessary for widespread adoption of LEDs for lighting. A review of the unique polarization anisotropy in GaN is included for the different crystal orientations. The emphasis on nonpolar and Semipolar LEDs highlights high-power violet and blue emitters, and we consider the effects of indium incorporation and well width. Semipolar GaN materials have enabled the development of high-efficiency LEDs in the blue region and recent achievements of green laser diodes at 520 nm.
Michel Khoury - One of the best experts on this subject based on the ideXlab platform.
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560 nm ingan micro leds on low defect density and scalable 20 21 Semipolar gan on patterned sapphire substrates
Optics Express, 2020Co-Authors: Michel Khoury, Shuji Nakamura, James S Speck, Jie Song, Haojun Zhang, Bastien Bonef, Tom Mates, Matthew S Wong, Joown Choi, Steven P. DenbaarsAbstract:We demonstrate InGaN-based Semipolar 560 nm micro-light-emitting diodes with 2.5% EQE on high-quality and low-defect-density (20-21) GaN templates grown on scalable and low-cost sapphire substrates. Through transmission electron microscopy observations, we discuss how the management of misfit dislocations and their confinement in areas away from the active light-emitting region is necessary for improving device performance. We also discuss how the patterning of Semipolar GaN on sapphire influences material properties in terms of surface roughness and undesired faceting in addition to indium segregation at the proximity of defected areas.
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efficient Semipolar 11 22 550 nm yellow green ingan light emitting diodes on low defect density 11 22 gan sapphire templates
ACS Applied Materials & Interfaces, 2017Co-Authors: Hongjian Li, Shuji Nakamura, Philippe De Mierry, Michel Khoury, Bastien Bonef, Abdullah I Alhassan, Asad J Mughal, Ezzah Azimah, M E A Samsudin, James S SpeckAbstract:We demonstrate efficient Semipolar (11–22) 550 nm yellow/green InGaN light-emitting diodes (LEDs) with In0.03Ga0.97N barriers on low defect density (11–22) GaN/patterned sapphire templates. The In0.03Ga0.97N barriers were clearly identified, and no InGaN clusters were observed by atom probe tomography measurements. The Semipolar (11–22) 550 nm InGaN LEDs (0.1 mm2 size) show an output power of 2.4 mW at 100 mA and a peak external quantum efficiency of 1.3% with a low efficiency drop. In addition, the LEDs exhibit a small blue-shift of only 11 nm as injection current increases from 5 to 100 mA. These results suggest the potential to produce high efficiency Semipolar InGaN LEDs with long emission wavelength on large-area sapphire substrates with economical feasibility.
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Efficient Semipolar (11–22) 550 nm Yellow/Green InGaN Light-Emitting Diodes on Low Defect Density (11–22) GaN/Sapphire Templates
2017Co-Authors: Michel Khoury, Shuji Nakamura, Philippe De Mierry, Bastien Bonef, Abdullah I Alhassan, Asad J Mughal, Ezzah Azimah, M E A Samsudin, James S SpeckAbstract:We demonstrate efficient Semipolar (11–22) 550 nm yellow/green InGaN light-emitting diodes (LEDs) with In0.03Ga0.97N barriers on low defect density (11–22) GaN/patterned sapphire templates. The In0.03Ga0.97N barriers were clearly identified, and no InGaN clusters were observed by atom probe tomography measurements. The Semipolar (11–22) 550 nm InGaN LEDs (0.1 mm2 size) show an output power of 2.4 mW at 100 mA and a peak external quantum efficiency of 1.3% with a low efficiency drop. In addition, the LEDs exhibit a small blue-shift of only 11 nm as injection current increases from 5 to 100 mA. These results suggest the potential to produce high efficiency Semipolar InGaN LEDs with long emission wavelength on large-area sapphire substrates with economical feasibility
