Exciton localization behaviour in different well width undoped GaN/Al0.07Ga0.93N nanostructures

2007 ◽  
Vol 15 (3) ◽  
Author(s):  
M. Sabooni ◽  
M. Esmaeili ◽  
H. Haratizadeh ◽  
B. Monemar ◽  
P. Paskov ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Decay Time ◽  
Photo Luminescence ◽  
Peak Position ◽  
Emission Peak ◽  
Time Resolved ◽  
Exciton Localization ◽  
Decay Times ◽  
Detection Energy ◽  
Hole Transition

AbstractWe report results from optical spectroscopy such as photoluminescence (PL) and time resolved photo-luminescence (TRPL) techniques from different well width MOCVD grown GaN/Al0.07Ga0.93N MQW samples. There is evidence of localization at low temperature in all samples. The decay time of all samples becomes non-exponential when the detection energy is increased with respect to the peak of the emission. Localization of carriers (excitons) is demonstrated by the “S-shape” dependences of the PL peak energies on the temperature. The time-resolved PL spectra of the 3-nm well multi quantum wells reveal that the spectral peak position shifts toward lower energies as the decay time increases and becomes red-shifted at longer decay times. There is a gradient in the PL decay time across the emission peak profile, so that the PL process at low temperatures is a free electron-localized hole transition.

Optical Study of Localized and Delocalized States in GaAsN/GaAs

2003 ◽  
Vol 798 ◽  
Author(s):  
Z. Y. Xu ◽  
X. D. Luo ◽  
X. D. Yang ◽  
P. H. Tan ◽  
C. L. Yang ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Rapid Thermal Annealing ◽  
Short Pulse ◽  
Selective Excitation ◽  
Excitation Power ◽  
Pulse Excitation ◽  
Optical Study ◽  
Time Resolved ◽  
Exciton Localization ◽  
Time Resolved Photoluminescence

ABSTRACTTaking advantages of short pulse excitation and time-resolved photoluminescence (PL), we have studied the exciton localization effect in a number of GaAsN alloys and GaAsN/GaAs quantum wells (QWs). In the PL spectra, an extra transition located at the higher energy side of the commonly reported N-related emissions is observed. By measuring PL dependence on temperature and excitation power along with PL dynamics study, the new PL peak has been identified as a transition of the band edge-related recombination in dilute GaAsN alloy and delocalized transition in QWs. Using selective excitation PL we further attribute the localized emission in QWs to the excitons localized at the GaAsN/GaAs interfaces. This interface-related exciton localization could be greatly reduced by a rapid thermal annealing.

scholarly journals Radiative Lifetime of Excitons in GaInN/GaN Quantum Wells

1996 ◽  
Vol 1 ◽  
Author(s):  
Jin Seo Im ◽  
Volker Härle ◽  
Ferdinand Scholz ◽  
Andreas Hangleiter
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Decay Time ◽  
Elevated Temperatures ◽  
Radiative Lifetime ◽  
Thermal Dissociation ◽  
Interface Roughness ◽  
Nonradiative Recombination ◽  
Quantum Well Structures ◽  
Decay Times

We have studied GaInN/GaN quantum well structures grown by LP-MOVPE by picosecond time-resolved photoluminescence spectroscopy. For the quantum wells we find rather long PL decay times of up to 600 ps at low temperature. At temperatures higher than about 100 K, the decay time decreases rapidly, reaching about 75 ps at room temperature. From measurements of the integrated PL intensity, we conclude that this decrease of the decay time is due to nonradiative recombination processes. By combining our data for the lifetime and the intensity, we derive the radiative lifetime, which is constant at low temperature and increases at elevated temperatures. We explain this behavior on the basis of the interface roughness at low temperature and thermal dissociation of excitons at higher temperatures.

Photo-Luminescence Dynamics of Ionic Liquids Composed of the Dicyanoaurate(I) Anion

2019 ◽  
Vol 72 (2) ◽  
pp. 42 ◽  
Author(s):  
Yoshifumi Kimura ◽  
Takamitsu Narita ◽  
Saki Tanaka ◽  
Mitsuhiro Taniguchi ◽  
Kaori Fujii ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Photo Luminescence ◽  
Wavelength Dependence ◽  
Structural Heterogeneity ◽  
Peak Shift ◽  
Peak Position ◽  
Time Profile ◽  
Excitation Wavelength ◽  
Time Resolved ◽  
The Difference

Time-resolved luminescent spectra of ionic liquids of 1-butyl-3-methylimidazolium dicyanoaurate ([C4mim][Au(CN)2]) and N-butyl-N-methylpyrrolidinium dicyanoaurate ([P14][Au(CN)2]) at different excitation wavelengths (310 and 340nm) were measured using a streak camera. Immediately after photoexcitation, an intense luminescence band appeared at ~380nm that rapidly decayed with a time constant of 31 ps for [C4mim][Au(CN)2] and 71 ps for [P14][Au(CN)2]. With the decay of this band, another luminescent band appeared at ~460nm that slowly decayed (88ns for [C4mim][Au(CN)2] and 1.2μs for [P14][Au(CN)2]). The peak position of this second band shifted to a longer wavelength over time for both ionic liquids. The time profile of the peak showed a multi-exponential decay and depended on the excitation wavelength and the cation species. The peak shift is discussed in terms of the aggregation of anions. The excitation wavelength dependence was supposed to reflect the distribution of the larger oligomer in the ground state and the structural heterogeneity of the ionic liquids. The difference as a result of the cation is discussed in relation to the viscosity and the structure of the ionic liquids.

scholarly journals GaInN/GaN-Heterostructures and Quantum Wells Grown by Metalorganic Vapor-Phase Epitaxy

1997 ◽  
Vol 2 ◽  
Author(s):  
A. Sohmer ◽  
J. Off ◽  
H. Bolay ◽  
V. Härle ◽  
V. Syganow ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Growth Parameters ◽  
Stokes Shift ◽  
Emission Peak ◽  
Band Edge ◽  
Time Resolved ◽  
Photothermal Deflection Spectroscopy ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Significant Line

The dependence of the In-incorporation efficiency and the optical properties of MOVPE-grown GaInN/GaN-heterostructures on various growth parameters has been investigated. A significant improvement of the In-incorporation rate could be obtained by increasing the growth rate and reducing the H2-partial pressure in the MOVPE reactor. However, GaInN layers with a high In-content typically show an additional low energy photoluminescence peak, whose distance to the band-edge increases with increasing In-content. For GaInN/GaN quantum wells with an In-content of approximately 12%, an increase of the well thickness is accompanied by a significant line broadening and a large increase of the Stokes shift between the emission peak and the band edge determined by photothermal deflection spectroscopy. With a further increase of the thickness of the GaInN layer, a second GaInN-correlated emission peak emerges. To elucidate the nature of these optical transitions, power-dependent as well as time-resolved photoluminescence measurements have been performed and compared to the results of scanning transmission electron microscopy.

Temperature and Time-Resolved Dependence of Photoluminescence in InGaN Quantum Dots

2013 ◽  
Vol 750-752 ◽  
pp. 927-930
Author(s):  
Cheng Chen ◽  
Zhi Ren Qiu ◽  
Xiang Ping Shu ◽  
Zeng Cheng Li ◽  
Jian Ping Liu ◽  
...  
Keyword(s):  
Decay Time ◽  
Peak Position ◽  
Localized States ◽  
Fast Decay ◽  
Time Resolved ◽  
Experimental Systems ◽  
Slow Decay ◽  
Double Exponential ◽  
Increasing Temperature ◽  
Time Resolved Photoluminescence

Temperature dependence of photoluminescence (PL) and time resolved photoluminescence (TRPL) were obtained by two experimental systems. The relative intensity and peak position of PL show S-shift variation with increasing temperature, which may result from temperature induce carriers redistribution. Fast decay time and slow decay time were fitted by double exponential function from decay curves of TRPL at different emission energy, and the decreasing trend of both fast decay and slow decay time with increasing photon energy is attributed to various channels of recombination in shallow and deep localized states.

Temperature Dependent and Time Resolved Optical Studies of Single Quantum Wells Produced by Interrupted Growth MBE

1986 ◽  
Vol 77 ◽  
Author(s):  
B. S. Elman ◽  
Emil S. Koteles ◽  
C. Jagannath ◽  
Y. J. Chen ◽  
S. Charbonneau ◽  
...  
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Single Quantum ◽  
Temperature Dependent ◽  
Time Resolved ◽  
Molecular Beam Epitaxial ◽  
Decay Times ◽  
Higher Temperature ◽  
The Individual ◽  
Molecular Beam Epitaxial Growth

ABSTRACTMultiple peaks, recently observed in the low temperature photoluminescence (PL) spectra of GaAs/AlGaAs single quantum wells fabricated by momentarily interrupting the molecular beam epitaxial growth between adjacent but different semiconductor layers, have been interpreted as originating within smooth regions in the quantum well layer differing in width by exactly one monolayer. We have observed similar structure in similarly grown samples but find that low temperature PL can be misleading. However, higher temperature PL or PL excitation spectroscopy do provide unambiguous evidence for the model of interface smoothing due to growth interruption. Further, time-resolved spectra yield decay times of the individual peaks which are consistent with this idea.

Optical Properties of Heavily Doped n-type CdSe Quantum Dots for Intersubband Device Applications

2006 ◽  
Vol 959 ◽  
Author(s):  
Shengkun Zhang ◽  
Xuecong Zhou ◽  
Aidong Shen ◽  
Wubao Wang ◽  
Robert Alfano ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Optical Properties ◽  
Quantum Wells ◽  
Ir Absorption ◽  
Cdse Quantum Dots ◽  
Nonradiative Recombination ◽  
Time Resolved ◽  
Luminescence Efficiency ◽  
Decay Times ◽  
Heavily Doped

ABSTRACTIn this research, interband and intersubband optical properties of heavily doped n-type CdSe quantum dots were investigated by temperature dependent photoluminescence (PL) spectroscopy, picosecond time-resolved PL spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Two doped and one undoped CdSe quantum dot samples with multiple QD layers were grown over ZnCdMgSe barrier layers on InP (001) substrate by molecular beam epitaxy. Heavy doping leads to decreasing of activation energy of nonradiative recombination centers, however, does not affect the luminescence efficiency of doped quantum wells. Time resolved PL experiments show that the PL decay times of the doped samples have weak dependence on well width and are much longer than that of the undoped sample. The two doped CdSe QD samples show strong Intersubband IR absorption that peaked at 2.54 μm, 2.69 μm and 3.51 μm. The ISB absorption is found to be strongly polarization dependent due to the large size of the QDs.

Time-resolved photoluminescence studies of InGaN/GaN multiple quantum wells

1997 ◽  
Vol 2 ◽  
Author(s):  
J. Allègre ◽  
P. Lefebvre ◽  
S. Juillaguet ◽  
W. Knap ◽  
J. Camassel ◽  
...  
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Multiple Quantum Well ◽  
Stimulated Emission ◽  
Multiple Quantum ◽  
Nitrogen Laser ◽  
Energy Position ◽  
Blue Band ◽  
Time Resolved ◽  
Decay Times

We report both cw and time resolved optical investigations performed on an InGaN/GaN multiple quantum well grown by MOVPE on <0001>-oriented sapphire substrate. At low temperature we find a strong “blue” luminescence band, of which energy position corresponds well with the wavelength of stimulated emission when excited with a nitrogen laser. We show that this PL band appears systematically red-shifted with respect to the QWs features, which supports a standard picture of fluctuations of the indium composition. Coming to the time-resolved data, we find at low temperature at least two “blue” band components which are both associated with long decay times (up to 4-5 ns at 8K). The decay time is temperature dependent and, when rising the temperature, the recombination rate increases. At room temperature, we reach typical values in the range ~100 to 500 ps.

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.

Effects of Piezoelectric Fields in GaInN/GaN and GaN/AlGaN Heterostructures and Quantum Wells

1997 ◽  
Vol 482 ◽  
Author(s):  
Jin Seo Im ◽  
H. Kollmer ◽  
J. Off ◽  
A. Sohmer ◽  
F. Scholz ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Quantitative Model ◽  
Emission Lines ◽  
Strong Increase ◽  
Time Resolved ◽  
Double Heterostructures ◽  
Decay Times ◽  
Piezoelectric Fields ◽  
Experimental Findings ◽  
Time Resolved Photoluminescence

AbstractThe effects of piezoelectric fields on the static and dynamic optical properties of GaInN/GaN and GaN/AIGaN double heterostructures and single quantum wells are studied by time-resolved photoluminescence. We find a strong increase of the luminescence decay time of the dominating transition with well thickness by several orders of magnitude. For well thicknesses larger than about 5 nm, two emission lines with strongly differing decay times are observed, which are attributed to spatially direct and indirect transitions. Our experimental findings are consistently explained by a quantitative model based on the piezoelectric fields in strained wurtzite quantum wells.

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