Exciton Lifetimes in GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
J.P. Bergman ◽  
C. Harris ◽  
B. Monemar ◽  
H. Amano ◽  
I. Akasaki
Keyword(s):  
Decay Time ◽  
Low Temperatures ◽  
Radiative Recombination ◽  
Radiative Lifetime ◽  
Free Exciton ◽  
Time Resolved ◽  
A Value ◽  
Donor And Acceptor ◽  
Exciton Recombination ◽  
Time Resolved Photoluminescence

ABSTRACTWe have performed time resolved photoluminescence measurements of the exciton recombination in different GaN samples at low temperatures. In epitaxial layers the decay time of the free exciton is typically faster than 100 ps. This is due to a dominating non-radiative recombination process. In thick bulk samples we have resolved and measured the decay time of the free exciton with a value of about 200 ps. We believe that this value is close to the radiative lifetime for free excitons in GaN. We have also shown that excitation transfer occurs between free and bound exciton states. We have furthermore measured the decay of the donor and acceptor bound excitons, and obtained values of the decay time of 250 ps and 1200 ps, respectively.

EXCITON LOCALIZATION IN (Cd,Zn)O EPILAYERS AND (Cd,Zn)O/(Mg,Zn)O MULTI-QUANTUM WELLS ON LATTICE-MATCHED SUBSTRATES

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3853-3856 ◽  
Author(s):  
T. MAKINO ◽  
N. T. TUAN ◽  
C. H. CHIA ◽  
Y. SEGAWA ◽  
M. KAWASAKI ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Radiative Recombination ◽  
Molecular Beam ◽  
Radiative Lifetime ◽  
Phonon Coupling ◽  
Time Resolved ◽  
Exciton Localization ◽  
Photoluminescence Studies ◽  
Time Resolved Photoluminescence ◽  
Lattice Matched

We report on optical properties of epitaxial (Cd,Zn)O layers and multi-quantum wells grown by laser molecular-beam epitaxy on lattice-matched ScAlMgO 4 substrates. Exciton-phonon coupling strength in (Cd,Zn)O layers estimated by temperature dependence of the excitonic energy was similar to that deduced in ZnO . Time-resolved photoluminescence studies were performed on the multi-quantum wells, which are almost perfectly lattice-matched (0.034%). Radiative recombination of excitons exhibits a spectral distribution of times. We found that the radiative lifetime increases linearly with temperature, showing a two-dimensional feature of excitons in quantum wells.

Time-Resolved Photoluminescence of CD(1-x)MN(x)SE and CD(1-x)MN(x)TE as a Function of Temperature

1986 ◽  
Vol 89 ◽  
Author(s):  
J. J. zayhowski ◽  
R. N. Kershaw ◽  
D. Ridgley ◽  
K. Dwight ◽  
A. Wold ◽  
...  
Keyword(s):  
Simple Model ◽  
Low Temperatures ◽  
Radiative Lifetime ◽  
Formation Time ◽  
Threshold Temperature ◽  
Magnetic Polaron ◽  
Time Resolved ◽  
Radiative Efficiency ◽  
Magnetic Polarons ◽  
Time Resolved Photoluminescence

AbstractThe characteristics of the photoluminescence of Cd(1-x)Mn(x)Se (x = 0.05, 0.10, 0.20, 0.30) and Cd(1-x)Mn(x)Te (x = 0.20, 0.30, 0.45) change considerably as the sample temperature is reduced below the exciton-magnetic polaron (EMP) threshold temperature. At low temperatures the formation of magnetic polarons has large effects on the luminescence energy, the radiative lifetime, the radiative efficiency, and the spectral half-width of the luminescence. It is also observed that the formation time of the EMP increases almost linearly with temperature. All of these effects are explained with a simple model for the EMP.

SELF-TRAPPED EXCITONS IN ORTHORHOMBIC SnBr2

2001 ◽  
Vol 15 (28n30) ◽  
pp. 4009-4012 ◽  
Author(s):  
Y. YAMASAKI ◽  
N. OHNO
Keyword(s):  
Time Dependence ◽  
Low Temperatures ◽  
Luminescence Band ◽  
Radiative Decay ◽  
Time Resolved ◽  
Tunneling Recombination ◽  
Exciton Region ◽  
Time Resolved Photoluminescence ◽  
Stokes Shifts ◽  
2.5 Ev Luminescence

Luminescence properties of SnBr 2 have been studied to reveal the photo-excited exciton relaxation process. Two types of luminescence with large Stokes shifts are found at low temperatures; the 2.2-eV luminescence band produced under the photo-excitation in the first exciton region, and the 2.5-eV luminescence band stimulated by photons with energies above the bandgap. The time-resolved photoluminescence measurements have revealed that the 2.2-eV luminescence comprises fast (1.2 μs) and slow (6.4 μs) exponential decay components, whereas the 2.5-eV luminescence shows the time dependence of I(t)∞ t-0.9. These results suggest that the former band is attributed to the radiative decay of self-trapped excitons, and the latter band would originate from tunneling recombination of holes with the STEL as in the case of lead halides.

scholarly journals Horizontal versus vertical charge and energy transfer in hybrid assemblies of semiconductor nanoparticles

2012 ◽  
Vol 3 ◽  
pp. 629-636 ◽  
Author(s):  
Gilad Gotesman ◽  
Rahamim Guliamov ◽  
Ron Naaman
Keyword(s):  
Energy Transfer ◽  
Charge Transfer ◽  
Horizontal Plane ◽  
Quartz Substrate ◽  
Vertical Direction ◽  
Time Resolved ◽  
Transfer Processes ◽  
Donor And Acceptor ◽  
Hybrid Assemblies ◽  
Time Resolved Photoluminescence

We studied the photoluminescence and time-resolved photoluminescence from self-assembled bilayers of donor and acceptor nanoparticles (NPs) adsorbed on a quartz substrate through organic linkers. Charge and energy transfer processes within the assemblies were investigated as a function of the length of the dithiolated linker (DT) between the donors and acceptors. We found an unusual linker-length-dependency in the emission of the donors. This dependency may be explained by charge and energy transfer processes in the vertical direction (from the donors to the acceptors) that depend strongly on charge transfer processes occurring in the horizontal plane (within the monolayer of the acceptor), namely, parallel to the substrate.

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.

EXCITONIC SIDE BANDS OF INNER-SHELL EXCITATIONS IN RARE GAS SOLIDS

2002 ◽  
Vol 09 (02) ◽  
pp. 1333-1338 ◽  
Author(s):  
S. VIELHAUER ◽  
M. KIRM ◽  
V. KISAND ◽  
E. NEGODIN ◽  
E. SOMBROWSKI ◽  
...  
Keyword(s):  
Free Exciton ◽  
Rare Gas ◽  
Excitation Threshold ◽  
Energy Position ◽  
Excitation Spectra ◽  
Electron Hole ◽  
Time Resolved ◽  
Ionization Limit ◽  
Time Resolved Photoluminescence ◽  
Hole Recombination

Valence-exciton luminescence under inner-shell excitation of the rare gas solids Xe, Kr, and Ar has been measured using time-resolved photoluminescence. Two different processes for exciton creation can be distinguished: creation of "prompt" excitons immediately after excitation (within the experimental time resolution), and creation of "delayed" excitons through electron–hole recombination. The decay structure of the exciton emission in the range of inner-shell excitation is characterized by the coexistence of the two processes. Time-resolved excitation spectra near the 2p edge in Ar, the 3d edge in Kr, and the 4d edge in Xe are discussed. The process of prompt exciton creation is strongly enhanced above an excitation threshold at the energy position of the ionization limit of the core state plus the energy of the valence free exciton.

UNDERSTANDING ULTRAVIOLET EMITTER PERFORMANCE USING INTENSITY DEPENDENT TIME-RESOLVED PHOTOLUMINESCENCE

2007 ◽  
Vol 17 (01) ◽  
pp. 179-188 ◽  
Author(s):  
MICHAEL WRABACK ◽  
GREGORY A. GARRETT ◽  
ANAND V. SAMPATH ◽  
PAUL H. SHEN
Keyword(s):  
Radiative Lifetime ◽  
Active Regions ◽  
Pump Intensity ◽  
Performance Comparison ◽  
Nonradiative Recombination ◽  
Extended Defects ◽  
Light Emitters ◽  
Time Resolved ◽  
Photoluminescence Studies ◽  
Time Resolved Photoluminescence

Time-resolved photoluminescence studies of nitride semiconductors and ultraviolet light emitters comprised of these materials are performed as a function of pump intensity as a means of understanding and evaluating device performance. Comparison of time-resolved photoluminescence (TRPL) on UV LED wafers prior to fabrication with subsequent device testing indicate that the best performance is attained from active regions that exhibit both reduced nonradiative recombination due to saturation of traps associated with point and extended defects and concomitant lowering of radiative lifetime with increasing carrier density. Similar behavior is observed in optically pumped UV lasers. Temperature and intensity dependent TRPL measurements on a new material, AlGaN containing nanoscale compositional inhomogeneities (NCI), show that it inherently combines inhibition of nonradiative recombination with reduction of radiative lifetime, providing a potentially higher efficiency UV emitter active region.

Subnanosecond transient studies of intrinsic and extrinsic luminescence in CdSe

1985 ◽  
Vol 63 (9) ◽  
pp. 1205-1211 ◽  
Author(s):  
T. Steiner ◽  
M. L. W. Thewalt
Keyword(s):  
Free Exciton ◽  
Exciton Luminescence ◽  
Time Resolved ◽  
Transient Behaviour ◽  
Doublet Structure ◽  
Donor And Acceptor ◽  
Optic Phonon ◽  
Longitudinal Optic ◽  
Low Levels ◽  
Longitudinal Optic Phonon

The photoluminescence spectrum and transient behaviour of free and bound excitons in CdSe have been studied with both resonant and above band-gap excitation. The free- and bound-exciton lifetimes were found to be excitation-intensity dependent even at very low levels. In all cases, the free-exciton luminescence decayed more rapidly than that of the bound excitons. A comparison of the no-phonon and longitudinal-optic-phonon replicas of the free-exciton luminescence indicates that the observed doublet structure of the no-phonon spectrum arises from the two polariton branches. Resonant excitation of the donor and acceptor bound excitons revealed two-electron and two-hole replicas, respectively. We believe these to be the first reported two-hole transitions in CdSe. The initial rapid cooling of the free-exciton gas could be observed in a series of time-resolved spectra.

Time-Resolved Photoluminescence of GaN / Ga0.93Al0 .07N Quantum Wells

1997 ◽  
Vol 482 ◽  
Author(s):  
P. Lefebvre ◽  
J. Allègre ◽  
B. Gil ◽  
A. Kavokine ◽  
H. Mathieu ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Radiative Lifetime ◽  
Temperature Limit ◽  
Multiple Quantum ◽  
Carrier Localization ◽  
Substantial Variation ◽  
Time Resolved ◽  
Potential Fluctuations ◽  
Alloy Disorder ◽  
Time Resolved Photoluminescence

AbstractThe recombination dynamics of excitons in GaN / Ga0.93Al0.07N multiple quantum wells is studied versus lattice temperature. The average decay time of photoluminescence measured at 8K is of ∼330 ps, with a substantial variation of times within the emission line. This is interpreted in terms of carrier localization due to alloy disorder and to well width and depth variations. The radiative lifetime τr of excitons in the wells is found to increase linearly with temperature, with ∂τr / ∂T = 20.5 ± 0.7 ps.K−1. The radiative lifetime of free excitons in the low-temperature limit is deduced to be 2.4 ps, consistent with a longitudinal-transverse splitting ћωLT in GaN of 0.6 meV, in excellent agreement with recent estimations. The ratio of the lifetimes of localized and free excitons is found coherent with the picture of electrons and holes independently localized on short-range defects, instead of excitons localized as a whole on long-range potential fluctuations.

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