Room Temperature Direct Band-Gap Emission from an Unstrained Ge P-I-N LED on Si

2011 ◽  
Vol 178-179 ◽  
pp. 25-30 ◽  
Author(s):  
Tzanimir Arguirov ◽  
Martin Kittler ◽  
Michael Oehme ◽  
Nikolay V. Abrosimov ◽  
Erich Kasper ◽  
...  
Keyword(s):  
Room Temperature ◽  
Bulk Material ◽  
Wave Length ◽  
Threading Dislocation ◽  
Strong Emission ◽  
Broad Energy Range ◽  
Threading Dislocation Density ◽  
Direct Band ◽  
Band Transition

We present a novel Ge on Si based LED with unstrained i-Ge active region. The device operates at room temperature and emits photons with energy of 0.8 eV. It basically resembles a p-i-n structure formed on a sub-micrometer thin Ge layer. The Ge layer has been grown on Si substrate by utilizing thin virtual buffer, so it becomes stress free but with high threading dislocation density. We show that such forward biased diode generates strong emission, caused by direct band to band transition in Ge. Using an InSb based detector we were able to analyze the emission spectrum in a broad energy range. We show that at low and moderate currents, features belonging to the direct and the indirect band to band electronic transitions are present which are characteristic for Ge. Clearly dominating is the direct transition related peak. Due to the missing stress-related red shift this peak appears close to the desired communication wave length of 1.55 μm. The dependence of radiation intensity on the excitation current follows a power low with exponent of 1.7, indicating that the recombination rate of the competitive nonradiative processes is relatively low. At high excitation currents features appear in the low energetic part of the spectrum. All results presented here are discussed in view of the outcome from measurements on Ge high quality bulk material. The role of the dislocation in the Ge films is discussed.

Role of substrate threading dislocation density in relaxation of highly strained InGaAs/GaAs quantum well structures

1990 ◽  
Vol 56 (14) ◽  
pp. 1350-1352 ◽  
Author(s):  
J. F. Klem ◽  
W. S. Fu ◽  
P. L. Gourley ◽  
E. D. Jones ◽  
T. M. Brennan ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Quantum Well ◽  
Threading Dislocation ◽  
Quantum Well Structures ◽  
Threading Dislocation Density ◽  
Highly Strained

Micro-Photoluminescence from V-shape inverted pyramid in HVPE Grown GaN Film

2002 ◽  
Vol 722 ◽  
Author(s):  
Chao-Kuei Lee ◽  
Y-B Chen ◽  
Shu-Chen Chang ◽  
Ci-Ling Pan ◽  
S. C. Wang
Keyword(s):  
Sapphire Substrate ◽  
Room Temperature ◽  
Threading Dislocation ◽  
Center Wavelength ◽  
Strong Emission ◽  
3 Dimensional ◽  
Inverted Pyramid ◽  
Excitation Laser ◽  
Piezoelectric Field ◽  
Gan Film

AbstractWe report the room-temperature micro-luminescence images from V-shaped inverted pyramids in undoped GaN films grown on (0001) sapphire substrate by hybrid vapor phase epitaxy. As the excitation laser spot at 325 nm was translated from the surface toward the center of the inverted pyramid along its slope, the center wavelength of the PL peak shows a trend of monotonic red-shift of from 373.9 nm to 379.1 nm. This could be attributed to the 3-dimensional release of stress and associated decrease of build-in piezoelectric field in the V-defects. A distinct and strong emission at 386.7 nm was observed at the apex of the V-defect. This could be originated from the threading dislocation at the onset of the defect.

scholarly journals LT-AlSb Interlayer as a Filter of Threading Dislocations in GaSb Grown on (001) GaAs Substrate Using MBE

Crystals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 628
Author(s):  
Agata Jasik ◽  
Jacek Ratajczak ◽  
Iwona Sankowska ◽  
Andrzej Wawro ◽  
Dariusz Smoczyński ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Low Temperature ◽  
Dislocation Density ◽  
Gaas Substrate ◽  
Periodic Array ◽  
Crystal Quality ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Threading Dislocation Density

We report on the role of AlSb material in the reduction of threading dislocation density (TDD) in the GaSb/AlSb/GaAs system. The AlSb layers were grown using low-temperature (LT) MBE, exploiting the interfacial misfit (IMF) dislocation array. AlSb layers with four different thicknesses in the range of 1–30 nm were investigated. The results showed the inhibiting role of LT-AlSb layers in the reduction of TDD. Values of TDD as low as 2.2 × 106 and 6.3 × 106 cm−2 for samples with thin and thick AlSb layers were obtained, respectively. The filtering role of AlSb material was proven despite the IMF-AlSb/GaAs interface’s imperfectness caused by the disturbance of a 90° dislocation periodic array by, most likely, 60° dislocations. The dislocation lines confined to the region of AlSb material were visible in HRTEM images. The highest crystal quality and smoother surface of 1.0 μm GaSb material were obtained using 9 nm thick AlSb interlayer. Unexpectedly, the comparative analysis of the results obtained for the GaSb/LT-AlSb/GaAs heterostructure and our best results for the GaSb/GaAs system showed that the latter can achieve both higher crystal quality and lower dislocation density.

Lattice imaging and pore structure of β ferric oxyhydroxide

1978 ◽  
Vol 36 (1) ◽  
pp. 264-265
Author(s):  
T. Baird ◽  
J.R. Fryer ◽  
S.T. Galbraith
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Bulk Material ◽  
Model Structure ◽  
Bulk Crystals ◽  
Lattice Imaging ◽  
Thin Sections ◽  
Ferric Oxyhydroxide ◽  
Resolution Electron ◽  
Hydrolysis Of

Introduction Previously we had suggested (l) that the striations observed in the pod shaped crystals of β FeOOH were an artefact of imaging in the electron microscope. Contrary to this adsorption measurements on bulk material had indicated the presence of some porosity and Gallagher (2) had proposed a model structure - based on the hollandite structure - showing the hollandite rods forming the sides of 30Å pores running the length of the crystal. Low resolution electron microscopy by Watson (3) on sectioned crystals embedded in methylmethacrylate had tended to support the existence of such pores.We have applied modern high resolution techniques to the bulk crystals and thin sections of them without confirming these earlier postulatesExperimental β FeOOH was prepared by room temperature hydrolysis of 0.01M solutions of FeCl3.6H2O, The precipitate was washed, dried in air, and embedded in Scandiplast resin. The sections were out on an LKB III Ultramicrotome to a thickness of about 500Å.

Clustering-Triggered Efficient Room Temperature Phosphorescence from Nonconventional Luminophores

2019 ◽  
Author(s):  
Shuyuan Zheng ◽  
Taiping Hu ◽  
Xin Bin ◽  
Yunzhong Wang ◽  
Yuanping Yi ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Efficiency ◽  
Spin Orbit Coupling ◽  
Design Rationale ◽  
Emission Mechanism ◽  
Room Temperature Phosphorescence ◽  
Electronic Interactions ◽  
Energy Gaps ◽  
Theoretical Results

Pure organic room temperature phosphorescence (RTP) and luminescence from nonconventional luminophores have gained increasing attention. However, it remains challenging to achieve efficient RTP from unorthodox luminophores, on account of the unsophisticated understanding of the emission mechanism. Here we propose a strategy to realize efficient RTP in nonconventional luminophores through incorporation of lone pairs together with clustering and effective electronic interactions. The former promotes spin-orbit coupling and boost the consequent intersystem crossing, whereas the latter narrows energy gaps and stabilizes the triplets, thus synergistically affording remarkable RTP. Experimental and theoretical results of urea and its derivatives verify the design rationale. Remarkably, RTP from thiourea solids with unprecedentedly high efficiency of up to 24.5% is obtained. Further control experiments testify the crucial role of through-space delocalization on the emission. These results would spur the future fabrication of nonconventional phosphors, and moreover should advance understanding of the underlying emission mechanism.<br>

Sewage sludge as a precursor of adsorbents/catalysts for environmental applications

2007 ◽  
Vol 2 (1) ◽  
Author(s):  
A. Ros ◽  
C. Canals-Batlle ◽  
M.A. Lillo-Ródenas ◽  
E. Fuente ◽  
M. A. Montes-Morán ◽  
...  
Keyword(s):  
Sewage Sludge ◽  
Room Temperature ◽  
Waste Water Treatment ◽  
Textural Properties ◽  
Active Species ◽  
Elemental Sulphur ◽  
Gaseous Emissions ◽  
Removal Experiments ◽  
Catalytically Active

This paper focuses on the valorisation of solid residues obtained from the thermal treatment of sewage sludge. In particular, sewage sludge samples were collected from two waste water treatment plants (WWTPs) with different sludge line basic operations. After drying, sludges were heated up to 700 °C in appropriate ovens under diluted air (gasification) and inert (pyrolysis) atmospheres. The solids obtained, as well as the dried (raw) sludges, were characterised to determine their textural properties and chemical composition, including the speciation of their inorganic fraction. All the materials under study were employed as adsorbents/catalysts in H2S removal experiments at room temperature. It was found that, depending on the particular sludge characteristics, outstanding results can be achieved both in terms of retention capacities and selectivity. Some of the solids outperform commercially available sorbents specially designed for gaseous emissions control. In these adsorbents/catalysts, H2S is selectively oxidised to elemental sulphur most likely due to the presence of inorganic, catalytically active species. The role of the carbon-enriched part on these solids is also remarked.

High-Irradiance Degradation Studies of Metamorphic 1eV GaInAs Solar Cells

2012 ◽  
Vol 1432 ◽  
Author(s):  
Ryan M. France ◽  
Myles A. Steiner
Keyword(s):  
Solar Cells ◽  
Active Region ◽  
Dislocation Density ◽  
Dark Current ◽  
Degradation Mechanism ◽  
Control Cell ◽  
High Irradiance ◽  
Threading Dislocation ◽  
Threading Dislocation Density ◽  
Degradation Studies

ABSTRACTInitial tests are performed regarding the degradation of lattice-mismatched GaInAs solar cells. 1eV metamorphic GaInAs solar cells with 1-2×106 cm-2 threading dislocation density in the active region are irradiated with an 808 nm laser for 2 weeks time under a variety of temperature and illumination conditions. All devices show a small degradation in Voc that is logarithmic with time. The absolute loss in performance after 2 weeks illuminated at 1300 suns equivalent and 125°C is 7 mV Voc and 0.2% efficiency, showing these devices to be relatively stable. The dark current increases with time and is analyzed with a two-diode model. A GaAs control cell degrades at the same rate, suggesting that the observed degradation mechanism is not related to the additional dislocations in the GaInAs devices.

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