Photoconductive Properties of GaAs1−xNx Double Heterostructures as a Function of Excitation Wavelength

1999 ◽  
Vol 607 ◽  
Author(s):  
R. K. Ahrenkiel ◽  
A. Mascarenhas ◽  
S. W. Johnston ◽  
Y Zhang ◽  
D. J. Friedman ◽  
...  
Keyword(s):  
Spectral Response ◽  
Nitrogen Addition ◽  
Excitation Wavelength ◽  
Band Model ◽  
Excitation Spectra ◽  
Recombination Lifetime ◽  
Double Heterostructures ◽  
Ternary Semiconductor ◽  
Bandgap Semiconductors ◽  
Recombination Lifetimes

AbstractThe ternary semiconductor GaAs1−xNx with 0 < x < 0.3 can be grown epitaxially on GaAs and has a very large bowing coefficient. The alloy bandgap can be reduced to about 1.0 eV with about a 3% nitrogen addition. In this work, we measlired the internal spectral response and recombination lifetime of a number of alloys using the ultra-high frequency photoconductive decay (UHFPCD) method. The data shows that the photoconductive excitation spectra of the GaAs0.97N0.03 alloy shows a gradual increase in response through the absorption edge near Eg. This contrasts with most direct bandgap semiconductors that show a steep onset of photoresponse at Eg. The recombination lifetimes frequently are much longer than expected from radiative recombination and often exceeded 1.0 µs. The data was analyzed in terms of a band model that includes large potential fluctuations in the conduction band due to the random distribution of nitrogen atoms in the alloy.

scholarly journals Excitation spectral microscopy for highly multiplexed fluorescence imaging and quantitative biosensing

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Kun Chen ◽  
Rui Yan ◽  
Limin Xiang ◽  
Ke Xu
Keyword(s):  
Fluorescence Imaging ◽  
Spectral Response ◽  
Fluorescence Emission ◽  
Resonance Energy ◽  
Spectral Width ◽  
Tunable Filter ◽  
Live Cells ◽  
Excitation Wavelength ◽  
Excitation Spectra ◽  
Multiplexed Fluorescence Imaging

AbstractThe multiplexing capability of fluorescence microscopy is severely limited by the broad fluorescence spectral width. Spectral imaging offers potential solutions, yet typical approaches to disperse the local emission spectra notably impede the attainable throughput. Here we show that using a single, fixed fluorescence emission detection band, through frame-synchronized fast scanning of the excitation wavelength from a white lamp via an acousto-optic tunable filter, up to six subcellular targets, labeled by common fluorophores of substantial spectral overlap, can be simultaneously imaged in live cells with low (~1%) crosstalks and high temporal resolutions (down to ~10 ms). The demonstrated capability to quantify the abundances of different fluorophores in the same sample through unmixing the excitation spectra next enables us to devise novel, quantitative imaging schemes for both bi-state and Förster resonance energy transfer fluorescent biosensors in live cells. We thus achieve high sensitivities and spatiotemporal resolutions in quantifying the mitochondrial matrix pH and intracellular macromolecular crowding, and further demonstrate, for the first time, the multiplexing of absolute pH imaging with three additional target organelles/proteins to elucidate the complex, Parkin-mediated mitophagy pathway. Together, excitation spectral microscopy provides exceptional opportunities for highly multiplexed fluorescence imaging. The prospect of acquiring fast spectral images without the need for fluorescence dispersion or care for the spectral response of the detector offers tremendous potential.

scholarly journals Excitation spectral microscopy for highly multiplexed fluorescence imaging and quantitative biosensing

2021 ◽  
Author(s):  
Kun Chen ◽  
Rui Yan ◽  
Limin Xiang ◽  
Ke Xu
Keyword(s):  
Fluorescence Imaging ◽  
Spectral Response ◽  
Fluorescence Emission ◽  
Resonance Energy ◽  
Spectral Width ◽  
Tunable Filter ◽  
Live Cells ◽  
Excitation Wavelength ◽  
Excitation Spectra ◽  
Multiplexed Fluorescence Imaging

The multiplexing capability of fluorescence microscopy is severely limited by the broad fluorescence spectral width. Spectral imaging offers potential solutions, yet typical approaches to disperse the local emission spectra notably impede the attainable throughput. Here we show that using a single, fixed fluorescence emission detection band, through frame-synchronized fast scanning of the excitation wavelength from a white lamp via an acousto-optic tunable filter (AOTF), up to 6 subcellular targets, labeled by common fluorophores of substantial spectral overlap, can be simultaneously imaged in live cells with low (~1%) crosstalks and high temporal resolutions (down to ~10 ms). The demonstrated capability to quantify the abundances of different fluorophores in the same sample through unmixing the excitation spectra next enables us to devise novel, quantitative imaging schemes for both bi-state and FRET (Forster resonance energy transfer) fluorescent biosensors in live cells. We thus achieve high sensitivities and spatiotemporal resolutions in quantifying the mitochondrial matrix pH and intracellular macromolecular crowding, and further demonstrate, for the first time, the multiplexing of absolute pH imaging with three additional target organelles/proteins to elucidate the complex, Parkin-mediated mitophagy pathway. Together, excitation spectral microscopy provides exceptional opportunities for highly multiplexed fluorescence imaging. The prospect of acquiring fast spectral images without the need for fluorescence dispersion or care for the spectral response of the detector offers tremendous potential.

scholarly journals Blackbody-sensitive room-temperature infrared photodetectors based on low-dimensional tellurium grown by chemical vapor deposition

2021 ◽  
Vol 7 (16) ◽  
pp. eabf7358
Author(s):  
Meng Peng ◽  
Runzhang Xie ◽  
Zhen Wang ◽  
Peng Wang ◽  
Fang Wang ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Spectral Response ◽  
Chemical Vapor ◽  
Hole Mobility ◽  
Infrared Detection ◽  
Infrared Photodetectors ◽  
Bandgap Semiconductors ◽  
Low Dimensional

Blackbody-sensitive room-temperature infrared detection is a notable development direction for future low-dimensional infrared photodetectors. However, because of the limitations of responsivity and spectral response range for low-dimensional narrow bandgap semiconductors, few low-dimensional infrared photodetectors exhibit blackbody sensitivity. Here, highly crystalline tellurium (Te) nanowires and two-dimensional nanosheets were synthesized by using chemical vapor deposition. The low-dimensional Te shows high hole mobility and broadband detection. The blackbody-sensitive infrared detection of Te devices was demonstrated. A high responsivity of 6650 A W−1 (at 1550-nm laser) and the blackbody responsivity of 5.19 A W−1 were achieved. High-resolution imaging based on Te photodetectors was successfully obtained. All the results suggest that the chemical vapor deposition–grown low-dimensional Te is one of the competitive candidates for sensitive focal-plane-array infrared photodetectors at room temperature.

Growth and Characterization of In-Based Nitride Compounds and their Double Heterostructures

1997 ◽  
Vol 468 ◽  
Author(s):  
V. A. Joshkin ◽  
J. C Roberts ◽  
E. L. Piner ◽  
M. K. Behbehani ◽  
F. G. McIntosh ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Growth Conditions ◽  
Excitation Power ◽  
Excitation Power Density ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
Recombination Lifetime ◽  
Pl Spectra ◽  
Double Heterostructures

ABSTRACTWe report on the growth and characterization of InGaN bulk films and AlGaN/InGaN/AlGaN double heterostructures (DHs). Good quality bulk InGaN films have been grown by metalorganic chemical vapor deposition (MOCVD) with up to 40% InN as characterized by x-ray diffraction. The effect of hydrogen in the growth ambient on the lnN% incorporation in the InGaN films is presented. Photoluminescence (PL) spectra of AlGaN/InGaN/AlGaN DHs exhibit emission wavelengths from the violet through yellow depending on the growth conditions of the active InGaN layer. The PL spectra are fairly broad both at room temperature and 20 K, and could be a result of native defects or impurity related transitions. We also observed a linear dependence between the PL intensity and excitation power density in the 0.001 W/cm2 to 10 MW/cm2 range. Time resolved PL of one of these DHs suggest a recombination lifetime on the order of 520 ps.

Excitation Energy-Dependent Transient Spectral Relaxation of Coumarin 153

1998 ◽  
Vol 52 (1) ◽  
pp. 82-90 ◽  
Author(s):  
W. C. Flory ◽  
G. J. Blanchard
Keyword(s):  
Excitation Energy ◽  
Spectral Response ◽  
Excitation Wavelength ◽  
Spectral Evolution ◽  
Relative Contribution ◽  
Coumarin 153 ◽  
Central Result ◽  
Spectral Relaxation ◽  
Evolution Behavior ◽  
Energy Dependent

We report on the excitation energy-dependent transient spectral response of the polar dye molecule coumarin 153 (C153) in selected solvents. We find that the blue edge of the spontaneous emission spectrum of C153 contains several spectral features and that the relative contribution of these features to the overall response varies with the identity of the solvent and the excitation wavelength. The central result of these data is that the transient spectral response of C153 depends sensitively on the excitation wavelength and that the spectral evolution behavior of this molecule is therefore not related in a simple manner to solvent reorganization dynamics.

scholarly journals Synthesis of Dy3+, Eu3+ and Tb3+ Activated Y2O2S Optoelectronic Phosphors for N-UV LED Applications

2020 ◽  
Vol 9 (4) ◽  
pp. 2068-2074
Keyword(s):  
Solid State Reaction Method ◽  
Yellow Emission ◽  
Strong Line ◽  
Excitation Wavelength ◽  
Excitation Spectra ◽  
Near Ultraviolet ◽  
Red Color ◽  
Blue Radiation ◽  
Bright Color ◽  
Color Emission

In this, a series of iso-structural Y2O2S (RE3+ = Dy3+ , Eu3+ and Tb3+) phosphors were synthesized by high temperature solid state reaction method. All the phosphors exhibit strong line and broad excitation in the near ultraviolet (n-UV) region. Bright color emission in blue, green and red color region of electromagnetic hue cycle was noticed. The concentration of activator doped was optimized from the photoluminescence (PL) study. The quenching in luminescence intensity after particular concentration of dopant is discussed here. Y2O2S phosphor doped with Dy3+displays useful blue and yellow emission bands at 487nm and 574nm, when stimulated by 388nm excitation wavelength. Y2O2S:Eu3+ phosphor displays an orange and red emission at 594nm and 620nm, when stimulated at 396 nm. Whereas, Y2O2S:Tb3+ phosphor displays weak blue radiation in the range 485nm and strong green radiation at 545nm, when stimulated at 305 nm. The excitation spectra used for the Y2O2S:RE3+ (RE3+ = Dy3+ , Eu3+ and Tb3+) phosphor is in the near ultraviolet (n-UV) region spanning from 300 nm to 400 nm, which is a peculiarity of near ultraviolet stimulated LED. The outcome of the RE3+ (RE3+= Dy3+ , Eu3+and Tb3+) absorption on the luminescence properties of Y2O2S:RE3+ phosphors was also studied.

Recombination lifetimes in undoped, low-band gap InAsyP1−y/InxGa1−xAs double heterostructures grown on InP substrates

2001 ◽  
Vol 78 (8) ◽  
pp. 1092-1094 ◽  
Author(s):  
R. K. Ahrenkiel ◽  
S. W. Johnston ◽  
J. D. Webb ◽  
L. M. Gedvilas ◽  
J. J. Carapella ◽  
...  
Keyword(s):  
Band Gap ◽  
Low Band Gap ◽  
Double Heterostructures ◽  
Recombination Lifetimes ◽  
Inp Substrates

scholarly journals RIGHT-ANGLE FLUORESCENCE SPECTROSCOPY FOR DIFFERENTIATION OF DISTILLED ALCOHOLIC BEVERAGES

2013 ◽  
Vol 12 (2) ◽  
pp. 83-92 ◽  
Author(s):  
Veronika Uríčková ◽  
Jana Sádecká ◽  
Pavel Májek
Keyword(s):  
Fluorescence Spectroscopy ◽  
Emission Spectra ◽  
Principal Component ◽  
Hierarchical Cluster ◽  
Alcoholic Beverages ◽  
Front Face ◽  
Excitation Wavelength ◽  
Spectroscopic Techniques ◽  
Excitation Spectra ◽  
Linear Discriminant

Abstract Total luminescence and synchronous scanning fluorescence spectroscopic techniques were investigated for differentiating brandies from mixed wine spirits. The studies were performed on 16 brandies from 3 different producers and 30 mixed wine spirits from 5 different producers. Differentiation between samples was accomplished by multivariate data analysis methods (principal component analysis, hierarchical cluster analysis, and linear discriminant analysis). Correct classification was obtained using emission spectra (400-650 nm) recorded at excitation wavelength 390 nm, excitation spectra (225-460 nm) obtained at emission wavelength 470 nm and synchronous fluorescence spectra (200-700 nm) collected at wavelength interval 80 nm. These results indicate that right-angle fluorescence spectroscopy offers a promising approach for the authentication of brandies as neither sample preparation nor special qualification of the personnel are required, and data acquisition and analysis are relatively simple when compared to front-face technique.

Strong room temperature 510 nm emission from cubic InGaN/GaN multiple quantum wells

2004 ◽  
Vol 831 ◽  
Author(s):  
S.F. Li ◽  
D.J. As ◽  
K. Lischka ◽  
D.G. Pacheco-Salazar ◽  
L.M.R. Scolfaro ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Room Temperature ◽  
Molecular Beam ◽  
Bandgap Energy ◽  
Multiple Quantum ◽  
Photoluminescence Intensity ◽  
Excitation Spectra ◽  
Room Temperature Photoluminescence ◽  
Double Heterostructures ◽  
Peak Energy

ABSTRACTCubic InGaN/GaN double heterostructures and multi-quantum-wells have been grown by Molecular Beam Epitaxy on cubic 3C-SiC. We find that the room temperature photoluminescence spectra of our samples has two emission peaks at 2.4 eV and 2.6 e V, respectively. The intensity of the 2.6 eV decreases and that of the 2.4 eV peak increases when the In mol ratio is varied between X = 0.04 and 0.16. However, for all samples the peak energy is far below the bandgap energy measured by photoluminescence excitation spectra, revealing a large Stokes-like shift of the InGaN emission. The temperature variation of the photoluminescence intensity yields an activation energy of 21 meV of the 2.6 eV emission and 67 meV of the 2.4 eV emission, respectively. The room temperature photoluminescence of fully strained multi quantum wells (x = 0.16) is a single line with a peak wavelength at about 510 nm.

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