Time Resolved Measurements of Radiative Recombination in GaAs/AIGaAs Heterostructures

1989 ◽  
Vol 160 ◽  
Author(s):  
J.P. Bergman ◽  
Q.X. Zhao ◽  
P.-O. Holtz ◽  
B. Monemar ◽  
M. Sundaram ◽  
...  
Keyword(s):  
Radiative Recombination ◽  
Three Dimensional ◽  
Gaas Layer ◽  
Excitation Intensity ◽  
Spectral Shape ◽  
Spectral Position ◽  
Experimental Conditions ◽  
Time Resolved ◽  
Decay Times ◽  
Time Resolved Photoluminescence

AbstractThe radiative recombination of two-dimensional (2D) carriers in an n-channel GaAs/AIGaAs heterojunction has been studied with time resolved photoluminescence (PL). Two bands related to the recombination of 2D carriers, the so called H-band 1 (HB1) and H-band 2 (HB2), are observed in PL. The spectral shape and position is strongly dependent on the sample and the experimental conditions. The H-bands are e.g. found to shift within a large energy range with the excitation intensity. We report here on the dependence of the decay times of the H-bands on their spectral position. The results are consistent with a recombination process involving 2D electrons, confined in the interface notch, and three-dimensional (3D) holes either from the valence band (HB1) or from neutral acceptors (HB2) in the active GaAs layer. The decay times of HB1 are found to vary in the range of 2-100 ns, while the corresponding decay times of HB2 are in the range of 100 ns - 10 µs.

Robust single-mode lasers based on hexagonal CdS microflakes

2020 ◽  
Vol 8 (32) ◽  
pp. 11201-11208
Author(s):  
Yang Mi ◽  
Yaoyao Wu ◽  
Jinchun Shi ◽  
Sheng-Nian Luo
Keyword(s):  
Radiative Recombination ◽  
Single Mode ◽  
Whispering Gallery Mode ◽  
Radiative Recombination Rate ◽  
Electron Hole ◽  
High Quality ◽  
Time Resolved ◽  
Whispering Gallery ◽  
Electron Hole Plasma ◽  
Time Resolved Photoluminescence

We have achieved single-mode whispering-gallery-mode lasing in CdS microflakes with sharp linewidth (∼0.12 nm) and high quality factor (∼4200). Such lasers are superior to previous CdS lasers in these lasing parameters. Through time-resolved photoluminescence measurements, electron–hole plasma recombination is established to be the lasing mechanism. The radiative recombination rate of CdS microflakes is enhanced by a factor of ∼4.7 due to the Purcell effect.

Preparation and Time Resolved Photoluminescence of Nanoscale InP Islands in In0.48Ga0.52P

1995 ◽  
Vol 379 ◽  
Author(s):  
K. Eberl ◽  
A. Kurtenbach ◽  
K. HÄusler ◽  
F. Noll ◽  
W.W. RÜhle
Keyword(s):  
Lattice Mismatch ◽  
Excitation Power ◽  
Buffer Layers ◽  
Time Resolved ◽  
Force Microscopy ◽  
Self Assembling ◽  
Atomic Force ◽  
Transmission Electron ◽  
Decay Times ◽  
Time Resolved Photoluminescence

ABSTRACTNanoscale InP islands are formed during InP/In0 48Ga0.52P heteroepitaxy due to the lattice mismatch of about 3.7%. The samples are prepared by solid source molecular beam epitaxy on (001) GaAs substrate. Atomic force microscopy measurements show that the size of the islands is typically 15 to 50 nm in diameter and about 5 to 10 nm high depending on the nominally deposited InP layer thickness, which is between 1 and 7.5 monolayers. Transmission electron micrographs show the coherent incorporation into the In0.48Ga0.52P matrix for InP islands with 2.5 monolayers. Resonantly excited time-resolved photoluminescence (PL) measurements of the self assembling InP dots are performed for optical characterisation. The decay times are typically 400 ps. The dependence on excitation power and temperature indicates the quantum dot nature of the InP islands. Finally a pronounced alignment of the InP islands is obtained on strained In0.61Ga0.39P buffer layers.

scholarly journals Long-range exciton diffusion in non-fullerene acceptors and coarse bulk heterojunctions enable highly efficient organic photovoltaics

2020 ◽  
Vol 8 (31) ◽  
pp. 15687-15694
Author(s):  
Muhammad T. Sajjad ◽  
Arvydas Ruseckas ◽  
Lethy Krishnan Jagadamma ◽  
Yiwei Zhang ◽  
Ifor D. W. Samuel
Keyword(s):  
Long Range ◽  
Organic Photovoltaics ◽  
Diffusion Length ◽  
Three Dimensional ◽  
Accurate Estimate ◽  
Bulk Heterojunctions ◽  
Time Resolved ◽  
Exciton Diffusion ◽  
Exciton Diffusion Length ◽  
Time Resolved Photoluminescence

Time-resolved photoluminescence measurements provide an accurate estimate of the three-dimensional exciton diffusion length in three ITICs based non-fullerene acceptors (NFAs).

White Light Luminescence from Nano-ZnS Doped Porous Silicon

2001 ◽  
Vol 686 ◽  
Author(s):  
K. W. Cheah ◽  
Ling Xu ◽  
Xinfan Huang
Keyword(s):  
Porous Silicon ◽  
White Light ◽  
Radiative Recombination ◽  
Surface States ◽  
Silicon Layer ◽  
Visible Spectrum ◽  
Porous Silicon Layer ◽  
Time Resolved ◽  
Direct Excitation ◽  
Time Resolved Photoluminescence

Nano-ZnS was deposited into porous silicon. By varying the concentration of Zn2+ ion solution during nano-ZnS formation, the amount of nano-ZnS in porous silicon host can be controlled. The doped porous silicon exhibited a gradual shift in its photoluminescence peak from red to blue as a function of the nano-ZnS coverage. At an optimum doping, white light photoluminescence was obtained. A study in the luminescence lifetime showed that the radiative recombination at the blue end of the visible spectrum was due to nano-ZnS, whereas, luminescence emission at the red end of the visible spectrum came from porous silicon. The latter luminescence was due to in part tunneling of excited electrons from nanoZnS into porous silicon and in part direct excitation of porous silicon layer. Time-resolved photoluminescence also showed that radiative recombination was effectively dominated by the nano-ZnS. Photoluminescence excitation result revealed the presence of two excitation levels; one belonged to nano-ZnS at near uv region, and another at about 520 nm from the surface states of porous silicon and nano-ZnS. The doping of nano-ZnS into porous silicon demonstrates that luminescence color tuning is possible when an appropriate functional material is introduced into porous silicon.

Probing biexciton in monolayer WS2 through controlled many-body interaction

2D Materials ◽  
2021 ◽  
Author(s):  
Suman Chatterjee ◽  
Sarthak Das ◽  
Garima Gupta ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
...  
Keyword(s):  
Radiative Recombination ◽  
Transition Metal Dichalcogenides ◽  
Excitation Power ◽  
Equation Model ◽  
Final States ◽  
Many Body ◽  
Time Resolved ◽  
Spectral Separation ◽  
Metal Dichalcogenides ◽  
Time Resolved Photoluminescence

Abstract The monolayers of semiconducting transition metal dichalcogenides host strongly bound excitonic complexes and are an excellent platform for exploring many-body physics. Here we demonstrate a controlled kinetic manipulation of the five-particle excitonic complex, the charged biexciton, through a systematic dependence of the biexciton peak on excitation power, gate voltage, and temperature using steady-state and time-resolved photoluminescence (PL). With the help of a combination of the experimental data and a rate equation model, we argue that the binding energy of the charged biexciton is less than the spectral separation of its peak from the neutral exciton. We also note that while the momentum-direct radiative recombination of the neutral exciton is restricted within the light cone, such restriction is relaxed for a charged biexciton recombination due to the presence of near-parallel excited and final states in the momentum space.

Luminescence Properties of Yb-Doped Inp

1993 ◽  
Vol 301 ◽  
Author(s):  
H. J. Lozykowski ◽  
A. K. Alshawa ◽  
G. Pomrenke ◽  
I. Brown
Keyword(s):  
Quantitative Agreement ◽  
Excitation Intensity ◽  
Photoluminescence Intensity ◽  
Photoluminescence Quenching ◽  
Time Resolved ◽  
Wide Range ◽  
Decay Times ◽  
Different Temperatures ◽  
First Time ◽  
Kinetics Of

ABSTRACTThe photoluminescence, time resolved spectra and kinetics of Yb implanted InP samples are studied under pulsed and CW excitations (above and below band-gap) at different temperatures and excitation intensity. The photoluminescence intensity and decay time as a function of temperature is explained by a proposed new quenching mechanism involving Fe ion. The rise and decay times depend on excitation intensity. The above experimental facts was explained using the kinetics model developed by H.J. Lozykowski [2]. The numerically simulated luminescence rise and decay times show a good quantitative agreement with experiment, over a wide range of generation rates. The electric field InP:Yb photoluminescence quenching was investigated and reported for the first time.

Time-Resolved Photoluminescence in a-Si1-xCx:H

1996 ◽  
Vol 420 ◽  
Author(s):  
Leandro R. Tessler ◽  
Lucicleide R. Cirino
Keyword(s):  
Low Power ◽  
Amorphous Silicon ◽  
Radiative Recombination ◽  
Room Temperature ◽  
Slow Component ◽  
Lifetime Distributions ◽  
Time Resolved ◽  
Recombination Mechanism ◽  
Silicon Carbon ◽  
Time Resolved Photoluminescence

AbstractThe dependence of the photoluminescence (PL) decay on temperature and composition of a series of amorphous silicon-carbon alloys (a-Si1-xCx:H) with 0 <x <0.4 was studied. The samples were prepared by “low power” PECVD from SiH4/CH4 gas mixtures. The decay curves are non-exponential and can be described as lifetime distributions (LTD). For pure a-Si:H at 17 K the peak of the LTD is of the order of 5×10-4 sec. It shifts to shorter lifetimes as x or the temperature increases. Samples with x > 0.3 present in addition a faster peak with maximum at 10-8 sec. The fast peak is almost temperature independent. The slow component shifts to shorter lifetimes as the temperature increases, and vanishes at room temperature. The presence of the fast peak is interpreted as due to a change in the radiative recombination mechanism. We associate this peak to the recombination of trapped “excitons”.

The Flow Field and Main Gas Ingestion in a Rotor-Stator Cavity

2007 ◽  
Author(s):  
R. P. Roy ◽  
D. W. Zhou ◽  
S. Ganesan ◽  
C.-Z. Wang ◽  
R. E. Paolillo ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Large Scale ◽  
Air Flow ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Radial Clearance ◽  
Air Flow Rate ◽  
Experimental Conditions ◽  
Time Resolved

The ingestion of mainstream gas into turbine rotor-stator disk cavities and simultaneously, the egress of cavity gas into the main gas path are consequences of the prevailing unsteady, three-dimensional flow field. To understand these processes, we are carrying out a study that combines experiments in a model single-stage axial turbine with computational fluid dynamic (CFD) simulations. The turbine stage features vanes, blades, and axially overlapping radial clearance rim seal. In this paper, we present time-resolved velocity maps, obtained by particle image velocimetry, of the flow in the disk cavity at four experimental conditions as defined by the main air flow rate, rotor speed, and purge air flow rate. Time-averaged but spatially local measurement of main air ingestion is also presented. Significant ingestion occurred at two of the four experimental conditions where the purge air flow rate was low — it is found that high tangential (swirl) velocity fluid intersperses with lower tangential velocity fluid in the rim region of the cavity. It is argued that the high tangential velocity fluid is comprised of the ingested main air, while the lower tangential velocity fluid is the indigenous cavity air. This interpretation is corroborated by the results of the unsteady, three-dimensional CFD simulation. When the purge flow rate was high, no ingestion occurred as expected; also, large-scale structures that were unsteady appeared in the cavity flow giving rise to large velocity fluctuations. It is necessary to obtain time-resolved information from experiments and computation in such a flow because even when the vane-blade relative position is matched during a particular experiment, the instantaneous flow field does not necessarily remain the same. As such, some of the flow patterns will be smeared out if the interrogation time scale is large.

scholarly journals Ферстеровский резонансный перенос энергии с участием светлых и темных экситонов в массивах эпитаксиальных квантовых точек CdSe/ZnSe

2018 ◽  
Vol 60 (8) ◽  
pp. 1575
Author(s):  
Т.Н. Михайлов ◽  
Е.А. Европейцев ◽  
К.Г. Беляев ◽  
A.A. Торопов ◽  
A.В. Родина ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excited States ◽  
Energy Transfer Process ◽  
Dipole Interaction ◽  
Energy Transfer Mechanism ◽  
Time Resolved ◽  
Decay Times ◽  
Förster Energy Transfer ◽  
Excitonic States ◽  
Time Resolved Photoluminescence

AbstractUsing time-resolved photoluminescence (PL) spectroscopy, we establish the presence of the Förster energy transfer mechanism between two arrays of epitaxial CdSe/ZnSe quantum dots (QDs) of different sizes. The mechanism operates through dipole–dipole interaction between ground excitonic states of the smaller QDs and excited states of the larger QDs. The dependence of energy transfer efficiency on the width of barrier separating the QD insets is shown to be in line with the Förster mechanism. The temperature dependence of the PL decay times and PL intensity suggests the involvement of dark excitons in the energy transfer process.

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