scholarly journals Micropyramid Vertical Ultraviolet GaN/AlGaN Multiple Quantum Wells LEDs on Si(111)

2021 ◽  
Vol 2021 ◽  
pp. 1-5
Author(s):  
Yuebo Liu ◽  
Honghui Liu ◽  
Hang Yang ◽  
Wanqing Yao ◽  
Fengge Wang ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Leakage Current ◽  
Light Emission ◽  
Uv Light ◽  
Multiple Quantum ◽  
Threading Dislocations ◽  
Nonradiative Recombination ◽  
Small Current ◽  
Uv Led ◽  
Optical Output

Micropyramid vertical GaN-based ultraviolet (UV) light-emitting diodes (LEDs) on Si(111) substrate have been fabricated by selective area growth to reduce threading dislocations and the polarization effects. There is no-light emission at the bottom and six planes of the pyramid at lower current due to the leakage current and nonradiative recombination of the dislocation at the bottom and the 90° threading dislocations (TDs) at six planes of the pyramid, and the top of the pyramid is the high-brightness region. The micropyramid UV LED has a high optical output intensity under a small current injection, and the series resistance of unit area is only a quarter of the conventional vertical LEDs, so the micropyramid UV LED would have a high output power under the drive circuit. The reverse leakage current of a single micropyramid UV LED is 2 nA at −10 V.

Origins and suppressions of parasitic emissions in ultraviolet light-emitting diode structures

2010 ◽  
Vol 25 (6) ◽  
pp. 1037-1040 ◽  
Author(s):  
Weihuang Yang ◽  
Shuping Li ◽  
Hangyang Chen ◽  
Dayi Liu ◽  
Junyong Kang
Keyword(s):  
Quantum Wells ◽  
Uv Light ◽  
Light Emitting Diode ◽  
Multiple Quantum ◽  
Light Emitting ◽  
Force Microscopy ◽  
Uv Led ◽  
Hole Blocking Layer ◽  
To Come ◽  
P Type

The AlGaN-based ultraviolet (UV) light-emitting diode (LED) structures with AlN as buffer were grown on sapphire substrate by metalorganic vapor-phase epitaxy (MOVPE). A series of cathodoluminescence (CL) spectra were measured from the cross section of the UV-LED structure using point-by-point sampling to investigate the origins of the broad parasitic emissions between 300 and 400 nm, and they were found to come from the n-type AlGaN and AlN layers rather than p-type AlGaN. The parasitic emissions were effectively suppressed by adding an n-type AlN as the hole-blocking layer. Electroluminescence (EL) and atomic force microscopy (AFM) measurements have revealed that the interface abruptness and crystalline quality of the UV-LED structure are essential for the achievement of the EL emissions from the multiple quantum wells (MQWs).

scholarly journals Coincident Electron Channeling and Cathodoluminescence Studies of Threading Dislocations in GaN

2013 ◽  
Vol 20 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Gunasekar Naresh-Kumar ◽  
Jochen Bruckbauer ◽  
Paul R. Edwards ◽  
Simon Kraeusel ◽  
Ben Hourahine ◽  
...  
Keyword(s):  
Structural Damage ◽  
Light Emission ◽  
Threading Dislocations ◽  
Nonradiative Recombination ◽  
Contrast Imaging ◽  
Force Microscopy ◽  
Electron Channeling ◽  
Microscopy Techniques ◽  
Cathodoluminescence Imaging ◽  
Edge Dislocations

AbstractWe combine two scanning electron microscopy techniques to investigate the influence of dislocations on the light emission from nitride semiconductors. Combining electron channeling contrast imaging and cathodoluminescence imaging enables both the structural and luminescence properties of a sample to be investigated without structural damage to the sample. The electron channeling contrast image is very sensitive to distortions of the crystal lattice, resulting in individual threading dislocations appearing as spots with black–white contrast. Dislocations giving rise to nonradiative recombination are observed as black spots in the cathodoluminescence image. Comparison of the images from exactly the same micron-scale region of a sample demonstrates a one-to-one correlation between the presence of single threading dislocations and resolved dark spots in the cathodoluminescence image. In addition, we have also obtained an atomic force microscopy image from the same region of the sample, which confirms that both pure edge dislocations and those with a screw component (i.e., screw and mixed dislocations) act as nonradiative recombination centers for the Si-doped c-plane GaN thin film investigated.

High-efficiency near-UV light-emitting diodes on Si substrates with InGaN/GaN/AlGaN/GaN multiple quantum wells

2020 ◽  
Vol 8 (3) ◽  
pp. 883-888 ◽  
Author(s):  
Yuan Li ◽  
Zhiheng Xing ◽  
Yulin Zheng ◽  
Xin Tang ◽  
Wentong Xie ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Quantum Efficiency ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Uv Light ◽  
Multiple Quantum ◽  
High Quantum Efficiency ◽  
Light Emitting ◽  
Si Substrates

High quantum efficiency LEDs with InGaN/GaN/AlGaN/GaN MQWs have been demonstrated. The proposed GaN interlayer barrier can not only increase the concentration and the spatial overlap of carriers, but also improve the quality of the MQWs.

scholarly journals Well-width dependence of radiative and nonradiative recombination times in ZnO/Mg0.12Zn0.88O multiple quantum wells

2001 ◽  
Vol 90 (7) ◽  
pp. 3650-3652 ◽  
Author(s):  
C. H. Chia ◽  
T. Makino ◽  
Y. Segawa ◽  
M. Kawasaki ◽  
A. Ohtomo ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Nonradiative Recombination

scholarly journals Comparison Study of Structural and Optical Properties of InxGa1−xN/GaN Quantum Wells with Different In Compositions

2000 ◽  
Vol 5 (S1) ◽  
pp. 977-983
Author(s):  
Yong-Hwan Kwon ◽  
G. H. Gainer ◽  
S. Bidnyk ◽  
Y. H. Cho ◽  
J. J. Song ◽  
...  
Keyword(s):  
Optical Properties ◽  
Quantum Wells ◽  
Chemical Vapor ◽  
Multiple Quantum ◽  
Nonradiative Recombination ◽  
X Ray Diffraction ◽  
Structural And Optical Properties ◽  
Recombination Rates ◽  
Satellite Peak ◽  
Interface Quality

The effect of In on the structural and optical properties of InxGa1−xN/GaN multiple quantum wells (MQWs) was investigated. These were five-period MQWs grown on sapphire by metalorganic chemical vapor deposition. Increasing the In composition caused broadening of the high-resolution x-ray diffraction superlattice satellite peak and the photoluminescence-excitation bandedge. This indicates that the higher In content degrades the interface quality because of nonuniform In incorporation into the GaN layer. However, the samples with higher In compositions have lower room temperature (RT) stimulated (SE) threshold densities and lower nonradiative recombination rates. The lower RT SE threshold densities of the higher In samples show that the suppression of nonradiative recombination by In overcomes the drawback of greater interface imperfection.

Temperature Dependence of Cathodoluminescence From InxGa1-xAs/GaAs Multiple Quantum Wells

1995 ◽  
Vol 379 ◽  
Author(s):  
K. Rammohan ◽  
D.H. Rich ◽  
A. Larsson
Keyword(s):  
Activation Energy ◽  
Quantum Wells ◽  
Temperature Dependence ◽  
Spatial Variations ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Nonradiative Recombination ◽  
Intensity Dependence ◽  
Thermally Activated

ABSTRACTThe temperature dependence of the cathodoluminescence (CL) originating from In0.21Ga0.79As/GaAs multiple quantum wells has been studied between 86 and 250 K. The CL intensity exhibits an Arrenhius-type dependence on temperature (T), characterized by two different activation energies. The spatial variations in activation energy caused by the presence of interfacial misfit dislocations is examined. The CL intensity dependence on temperature for T ≲ 150 K is controlled by thermally activated nonradiative recombination. For T ≳ 150 K the decrease in CL intensity is largely influenced by thermal re-emission of carriers out of the quantum wells.

Optical Spectroscopy of Defects in GaAs/AlGaAs Multiple Quantum Wells.

1993 ◽  
Vol 325 ◽  
Author(s):  
B. Monemar ◽  
P. O. Holtz ◽  
J. P. Bergman ◽  
Q.X. Zhao ◽  
C.I. Harris ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Optical Spectroscopy ◽  
Thermal Emission ◽  
Deep Level ◽  
Free Exciton ◽  
Interface Roughness ◽  
Multiple Quantum ◽  
Nonradiative Recombination ◽  
Decay Times ◽  
Bulk Semiconductors

AbstractThe study of electronic properties of GaAs/AlGaAs quantum wells (QWs) has traditionally been focused on intrinsic phenomena, in particular the free exciton behaviour. Defects and impurities have often been regarded as less relevant compared to the case of bulk semiconductors. Doping in QWs is important in many applications, however, and recently the knowledge about the structure of shallow donors and acceptors from optical spectroscopy has advanced to a level comparable to the situation in bulk semiconductors. A dramatic difference from the bulk case is the common occurrence of localisation effects due to interface roughness in QW structures. The recombination of bound excitons (BEs) differs drastically from bulk, BE lifetimes decrease with decreasing well thickness Lw, but increase with decreasing barrier thickness Lb (at constant Lw) below Lb=70Å. Exciton capture at impurities is a process which is strongly influenced by the localisation potentials from the interface roughness. The recombination process in doped QWs involves a nonradiative component, for shallow acceptors an excitonic Auger process has been identified. Deep nonradiative defects in the (MBE grown) QW as well as in the barrier material are manifested in measurements of the PL decay time vs temperature. In undoped multiple QWs the decay times vs T are consistent with thermal emission out of the well into the barrier, where nonradiative recombination via deep level defects occur. Nonradiative recombination in the well itself can be studied in electron-irradiated structures. Preliminary data also demonstrate the feasibility of hydrogen passivation of dopants as well as deep levels in the QW structures.

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