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.

Recombination Dynamics of Surface-Related Excitonic States in Single ZnO Nanowires

2008 ◽  
Vol 8 (1) ◽  
pp. 228-232 ◽  
Author(s):  
Tobias Voss ◽  
Lars Wischmeier
Keyword(s):  
Low Temperatures ◽  
Optical Spectra ◽  
Semiconductor Nanowires ◽  
Emission Lines ◽  
Time Resolved ◽  
Photoluminescence Studies ◽  
Different Diameters ◽  
Excitonic States ◽  
Time Resolved Photoluminescence ◽  
Recombination Dynamics

With decreasing diameter the influence of surface-related effects becomes increasingly important for an understanding of the optical properties of semiconductor nanowires. We present time integrated and time resolved photoluminescence studies of single zincoxide nanowires with different diameters. We analyze the changes in the optical spectra for wires with different surface-to-volume ratios, present optical spectra of single wires at different excitation densities, and study the time-resolved dynamics of the surface related and donor-bound exciton related emission lines for a single nanowire at low temperatures.

TIME-RESOLVED PHOTOLUMINESCENCE OF EXCITONS IN HgI2

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3920-3923 ◽  
Author(s):  
N. OHNO ◽  
X. M. WEN
Keyword(s):  
Radiative Recombination ◽  
Luminescence Band ◽  
Broad Band ◽  
Relaxation Processes ◽  
Time Resolved ◽  
Carrier Lifetimes ◽  
Broad Luminescence Band ◽  
Donor Acceptor ◽  
Exciton Annihilation ◽  
Time Resolved Photoluminescence

The time-resolved photoluminescence (TRPL) of red HgI 2 single crystal has been measured to determine the carrier lifetimes and to reveal the energy relaxation of excitons. Sharp near-bandgap luminescence lines due to free and bound excitons are observed at 530 nm, and a broad luminescence band appears at 630 nm at low temperatures. TRPL experiments of the near-bandgap luminescence have revealed that the luminescence comprise fast (30 to 200 ps) and slow (100 to 400 ps) decay components, showing several relaxation processes in free and bound exciton annihilation. TRPL of the broad band at 630 nm has shown that the luminescence is ascribed to the radiative recombination of donor-acceptor (DA) pairs.

Time Resolved Photoluminescence of Yb in InP

1987 ◽  
Vol 104 ◽  
Author(s):  
P. B. Klein
Keyword(s):  
Activation Energy ◽  
Valence Band ◽  
Low Temperatures ◽  
Weak Coupling ◽  
Thermal Activation ◽  
Thermal Activation Energy ◽  
Excited State Lifetime ◽  
Time Resolved ◽  
Exponential Component ◽  
Time Resolved Photoluminescence

ABSTRACTTime resolved photoluminescence (PL) measurements of the internal 4f-4f transitions of Yb3+ have been carried out in InP and GaP. In InP a nonexponential component is observed in the PL decay, and is interpreted in terms of carrier capture by nonequilibrium Yb3+. At low temperatures the exponential component is found to be much faster (≈12.5 μsec) than expected, and is tentatively associated with a weak coupling to resonant valence band states. As the temperature is increased, the PL intensity and the exponential component of the excited state lifetime are quenched with a thermal activation energy of ≈0.1 eV. This is interpreted as being due to the emission of a hole into the valence band by the neutral Yb acceptor.

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.

Time Resolved Photoluminescence Spectroscopy on GaN Epitaxial Layers

1995 ◽  
Vol 378 ◽  
Author(s):  
B. K. Meyer ◽  
D. Volm ◽  
C. Wetzel ◽  
L. Eckey ◽  
J.-Ch. Holst ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Photoluminescence Spectroscopy ◽  
Epitaxial Layers ◽  
Acceptor Pair ◽  
Time Resolved ◽  
Sapphire Substrates ◽  
Donor Acceptor ◽  
Donor Acceptor Pair ◽  
Time Resolved Photoluminescence

AbstractFree and bound exciton luminescences as well as donor-acceptor pair recombination of GaN epitaxial layers on 6H-SiC and sapphire substrates were investigated using time integrated and time resolved photoluminescence measurements at low temperatures. Lifetimes are determined for the donor bound exciton at 3.4722eV and for two acceptor bound excitons with energies of 3.4672eV and 3.459eV. Luminescences between 3.29eV and 3.37eV are identified as due to excitons deeply bound to centers located near the substrate-epilayer interface.

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 dynamics in thick GaN MOVPE epilayers deposited on sapphire.

1997 ◽  
Vol 2 ◽  
Author(s):  
J. Allègre ◽  
P. Lefebvre ◽  
J. Camassel ◽  
B. Beaumont ◽  
Pierre Gibart
Keyword(s):  
Layer Thickness ◽  
Buffer Layers ◽  
Rate Equations ◽  
Time Resolved ◽  
Versus Layer ◽  
Level Model ◽  
Shallow Impurities ◽  
Aln Buffer ◽  
Time Resolved Photoluminescence

Time-resolved photoluminescence spectra have been recorded on three GaN epitaxial layers of thickness 2.5 μm, 7 μm and 16 μm, at various temperatures ranging from 8K to 300K. The layers were deposited by MOVPE on (0001) sapphire substrates with standard AlN buffer layers. To achieve good homogeneities, the growth was in-situ monitored by laser reflectometry. All GaN layers showed sharp excitonic peaks in cw PL and three excitonic contributions were seen by reflectivity. The recombination dynamics of excitons depends strongly upon the layer thickness. For the thinnest layer, exponential decays with τ ~ 35 ps have been measured for both XA and XB free excitons. For the thickest layer, the decay becomes biexponential with τ1 ~ 80 ps and τ2 ~ 250 ps. These values are preserved up to room temperature. By solving coupled rate equations in a four-level model, this evolution is interpreted in terms of the reduction of density of both shallow impurities and deep traps, versus layer thickness, roughly following a L−1 law.

ZnCdO/ZnMgO and ZnO/AlGaN Heterostructures for UV and Visible Light Emitters

2005 ◽  
Vol 892 ◽  
Author(s):  
Andrei Osinsky ◽  
Jianwei Dong ◽  
J. Q. Xie ◽  
B. Hertog ◽  
A. M. Dabiran ◽  
...  
Keyword(s):  
Molecular Beam ◽  
Compositional Analysis ◽  
Optical Emission ◽  
Rf Plasma ◽  
Light Emitters ◽  
Time Resolved ◽  
Light Emitting ◽  
Spatially Resolved ◽  
Time Resolved Photoluminescence ◽  
Made In

AbstractThis paper reviews of some of the progress made in the development of ZnO-based light emitting diodes (LEDs). n-ZnO/p-AlGaN-based heterostructures have been successfully for the fabrication of UV emitting LEDs that have operated at temperatures up to 650K, suggesting an excitonic origin for the optical transitions. RF-plasma-assisted molecular beam epitaxy has been used to grow epitaxial CdxZn1-xO films on GaN/sapphire structure. These films have a single-crystal wurtzite structure as demonstrated by structural and compositional analysis. High quality CdxZn1-xO films were grown with up to x=0.78 mole fraction as determined by RBS and SIMS techniques. Optical emission ranging from purple (Cd0.05Zn0.95O) to yellow (Cd0.29Zn0.71O) was observed. Compositional fluctuations in a Cd0.16Zn0.84O films were not detected by spatially resolved CL measurements, although intensity fluctuation with features of ∼0.5 μm diameter were seen on the intensity maps. Time resolved photoluminescence shows multi-exponential decay with 21 psec. and 49±3 psec. lifetimes, suggesting that composition micro-fluctuations may be present in Cd0.16Zn0.84O film.

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