scholarly journals Optical Spectroscopy of Ingan Epilayers in the Low Indium Composition Regime

2000 ◽  
Vol 5 (S1) ◽  
pp. 717-724
Author(s):  
M. H. Crawford ◽  
J. Han ◽  
M. A. Banas ◽  
S. M. Myers ◽  
G. A. Petersen ◽  
...  
Keyword(s):  
Room Temperature ◽  
Radiative Decay ◽  
Thermal Quenching ◽  
Localized States ◽  
Spectral Variation ◽  
Temperature Dependent ◽  
Time Resolved ◽  
Decay Times ◽  
Integrated Intensity ◽  
Si Doped

Photoluminescence (PL) spectroscopy was carried out on a series of Si-doped bulk InGaN films in the low indium (In) composition regime. Room temperature PL showed a factor of 25 increase in integrated intensity as the In composition was increased from 0 to 0.07. Temperature dependent PL data was fit to an Arrhenius equation to reveal an increasing activation energy for thermal quenching of the PL intensity as the In composition is increased. Time resolved PL measurements revealed that only the sample with highest In (x=0.07) showed a strong spectral variation in decay time across the T=4K PL resonance, indicative of recombination from localized states at low temperatures. The decay times at room temperature were non-radiatively dominated for all films, and the room temperature (non-radiative) decay times increased with increasing In, from 50-230 psec for x=0-0.07. Our data demonstrate that non-radiative recombination is less effective with increasing In composition.

scholarly journals Optical Spectroscopy of Ingan Epilayers in the Low Indium Composition Regime

1999 ◽  
Vol 595 ◽  
Author(s):  
M. H. Crawford ◽  
J. Han ◽  
M. A. Banas ◽  
S. M. Myers ◽  
G. A. Petersen ◽  
...  
Keyword(s):  
Room Temperature ◽  
Radiative Decay ◽  
Thermal Quenching ◽  
Localized States ◽  
Spectral Variation ◽  
Temperature Dependent ◽  
Time Resolved ◽  
Decay Times ◽  
Integrated Intensity ◽  
Si Doped

AbstractPhotoluminescence (PL) spectroscopy was carried out on a series of Si-doped bulk InGaN films in the low indium (In) composition regime. Room temperature PL showed a factor of 25 increase in integrated intensity as the In composition was increased from 0 to 0.07. Temperature dependent PL data was fit to an Arrhenius equation to reveal an increasing activation energy for thermal quenching of the PL intensity as the In composition is increased. Time resolved PL measurements revealed that only the sample with highest In ( x=0.07) showed a strong spectral variation in decay time across the T=4K PL resonance, indicative of recombination from localized states at low temperatures. The decay times at room temperature were non-radiatively dominated for all films, and the room temperature (non-radiative) decay times increased with increasing In, from 50-230 psec for x=0-0.07. Our data demonstrate that non-radiative recombination is less effective with increasing In composition.

scholarly journals Time Resolved Photoluminescence of Si-doped High Al Mole Fraction AlGaN Epilayers Grown by Plasma-Enhanced Molecular Beam Epitaxy

2003 ◽  
Vol 798 ◽  
Author(s):  
Madalina Furis ◽  
Alexander N. Cartwright ◽  
Jeonghyun Hwang ◽  
William J. Schaff
Keyword(s):  
Mole Fraction ◽  
Slow Component ◽  
Localized States ◽  
Yellow Emission ◽  
Alloy Formation ◽  
Temperature Dependent ◽  
Time Resolved ◽  
Si Doped ◽  
Pl Spectrum ◽  
Time Resolved Photoluminescence

ABSTRACTWe report on detailed temperature dependent, time-resolved photoluminescence (TRPL) studies of Si-doped AlGaN epilayers. In these samples, the Al concentration varies from 25% to 66%. The samples were found to exhibit metallic-like temperature-independent conductivity. The deep level “yellow” emission, whose presence would indicate the existence of a large number of defects associated with growth, Si incorporation, and/or alloy formation, is absent. In addition to emission corresponding to the donor-bound exciton, the PL spectrum exhibits features associated with transitions involving localized carriers. This assignment of the emission mechanisms is based on the activation energies extracted from the temperature dependent photoluminescence (PL) quenching. Specifically, at room temperature the PL spectrum is dominated by transitions involving localized states. The localization energy varied from sample to sample and was observed to be between 115 meV to 200 meV. The PL intensity decay in the lower Al mole fraction epilayers exhibits a slow component associated with the presence of donor-bound excitons.

scholarly journals Optical Characterization of Erbium Doped III-Nitrides Prepared by Metalorganic Molecular Beam Epitaxy

1999 ◽  
Vol 4 (S1) ◽  
pp. 952-961 ◽  
Author(s):  
U. Hömmerich ◽  
J. T. Seo ◽  
Myo Thaik ◽  
J. D. MacKenzie ◽  
C. R. Abernathy ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Room Temperature ◽  
Molecular Beam ◽  
Radiative Decay ◽  
Thermal Quenching ◽  
Low Oxygen ◽  
Absorption Bands ◽  
Metalorganic Molecular Beam Epitaxy ◽  
Pl Intensity ◽  
Carbon Concentrations

We are currently engaged in a systematic study of the optical properties of Er doped III-nitrides prepared by metalorganic molecular beam epitaxy (MOMBE). Under below-gap excitation it was observed that GaN: Er samples with [O]∼1020 cm−3 and [C]∼1021 cm−3 luminesce at 1540 nm with an intensity of more than two orders of magnitude greater than samples with low oxygen and carbon concentrations (< 1019 cm−3). Associated with the different oxygen and carbon concentrations were different thermal quenching behaviors and below-gap absorption bands. Interestingly, for above-gap excitation only small differences in absolute Er3+ PL intensity and quenching behavior were observed for samples of varying O and C content. Initial lifetime studies were performed and showed a rather unusual short decay time of ∼100 μs at room temperature. In order to gain more insight in the Er3+ PL, a comparison of the integrated PL intensity and lifetime was performed for the temperature range 15-500K. The result reveals that the Er3+ PL quenches above room temperature due to the onset of non-radiative decay and the reduction in excitation efficiency. All samples were also investigated for visible luminescence. Red luminescence was observed from GaN: Er on sapphire substrates under below-gap excitation.

Lattice Location and Cathodoluminescence Studies of Ytterbium/Thulium Implanted 2H-Aluminium Nitride

2002 ◽  
Vol 743 ◽  
Author(s):  
U. Vetter ◽  
M. F. Reid ◽  
H. Hofsäss ◽  
C. Ronning ◽  
J. Zenneck ◽  
...  
Keyword(s):  
Room Temperature ◽  
Lattice Site ◽  
Electron Transition ◽  
Lattice Location ◽  
Temperature Dependent ◽  
Time Resolved ◽  
Annealing Temperatures ◽  
Visible Luminescence ◽  
On Line ◽  
Emission Channeling

ABSTRACTLattice location studies of radioactive 169Yb ions, implanted at an energy of 60 keV into 2H-AlN at the on-line isotope separator ISOLDE at CERN, were performed using the emission channeling technique. The measurements, which yield a substitutional Al lattice site for the implanted ions, were recorded for annealing temperatures ranging from 293 K to 1273 K. After complete decay of 169Yb to 169Tm cathodoluminescence measurements were performed in the range 12 K – 300 K. The samples show a strong visible luminescence at 460 - 470 nm at room temperature, which is attributed to the 1D2−3F4 intra-4f electron transition of Tm3+. At 12 K the luminescence is dominated by transitions starting from the 1H6 multiplet. Time resolved as well as temperature dependent cathodoluminescence measurements are presented and discussed.The lattice location as well as the time resolved cathodoluminescence measurements suggest that there is only one pronounced site of the implanted ions in the AlN lattice and that this is the substitutional aluminium site.

Radiative Recombination and Carrier Lifetimes in Surface-Free GaAs Homostructures

1989 ◽  
Vol 163 ◽  
Author(s):  
L. M. Smith ◽  
D. J. Wolford ◽  
R. Venkatasubramanian ◽  
S.K. Ghandhi
Keyword(s):  
Room Temperature ◽  
Diffusion Constant ◽  
Near Band Edge ◽  
Time Resolved ◽  
Bulk Gaas ◽  
Carrier Lifetimes ◽  
Double Heterostructures ◽  
Order Of Magnitude ◽  
Si Doped ◽  
P Type

AbstractWe show that the radiative efficiencies and lifetimes of photoexcited carriers in epitaxial GaAs may be enhanced by 3 to 4 orders-of-magnitude by the preparation of n+, doped layers at surface and substrate interfaces. Samples were prepared by Organo-Metallic Vapor Phase Epitaxy (OMVPE), with n-region thicknesses of 3–10 µm, and narrow layers Si-doped to n+ concentrations of 5×1018 cm-3. Time-resolved luminescence in such structures, under both surface and bulk (near-band-edge) excitation conditions, reveal near-edge-excitonic or band-to-band-dominated recombination spectra, with carrier lifetimes ranging from 1.5 nsec at 1.5 K to nearly 1 µsec at room temperature. This is in contrast to the sub-nanosecond lifetimes typical in conventionally prepared bulk GaAs, but is comparable to the best reported for high-purity LPE-prepared GaAs/AlxGa1-xAs double heterostructures. The spatial distributions of photoexcited carriers in these structures are observed to expand by over an order of magnitude during their 1 µsec room temperature lifetime. The expansion is diffusive, with a measured diffusion constant of 14 cm2/sec at 300 K. This corresponds to a room temperature mobility of 525 cm2/Vsec, comparable to previously measured hole mobilities in bulk p-type GaAs of similar purity. These results are clear evidence that the narrow, heavily doped layers effectively “shield” minority carriers from the interfaces, thereby reducing interface recombination.

Steady-state and Time-resolved Spectroscopic Studies of Benzanilides

1999 ◽  
Vol 54 (8-9) ◽  
pp. 495-502 ◽  
Author(s):  
Józef Heldt ◽  
Janina R. Heldt ◽  
Jerzy Kamiński
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Steady State ◽  
Proton Transfer ◽  
Room Temperature ◽  
Spectroscopic Studies ◽  
Fluorescence Band ◽  
Polar Solvents ◽  
Time Resolved ◽  
Decay Times

Steady-state and time-resolved spectroscopic studies of benzanilide (I) and jV-methylbenzanilide (II)were performed at 298 and 77 K in various solvents. The results indicate that benzanilide fluorescencein non-polar solvents at room temperature involves three independent modes of emission: F1 (LE) normalfluorescence from the initially excited state S1 (LE) with λmax = 320 nm, F2´(PT) fluorescence from the proton transfer tautomer with λmax = 468 nm, F2″CT) fluorescence from the species where intramolecular charge transfer appears, with λmax = 510 nm. At 77 K in MCH a new fluorescence band, Fag, appears at λmax=415 nm instead of the F2(PT) and F2″CT) fluorescence. This new emission originates from benzanilide dipolar aggregates or cis-imidol dimers. The decay times of these emission modes aredifferent.N-methylbenzanilide, dissolved in nonpopular and weakly polar solvents at room temperature and at77 K, shows only two fluorescence modes, i.e., the normal and the charge-transfer emissions at 320 nmand 520 nm, respectively. The fluorescence is deactivated with two decay times, 30 ps and 2.05 ns, inMCH solution.

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 Zn0.46Cd0.54Se/Zn0.24Cd0.25Mg0.51Se Multiple Quantum Wells for Infrared Photodetector Applications

2006 ◽  
Vol 952 ◽  
Author(s):  
Xuecong Zhou ◽  
Shengkun Zhang ◽  
Hong Lu ◽  
Aidong Shen ◽  
Wubao Wang ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Quantum Cascade Lasers ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Infrared Photodetector ◽  
Temperature Dependent ◽  
Time Resolved ◽  
Mid Infrared ◽  
Luminescence Efficiency ◽  
Decay Times

ABSTRACTRecently, lattice-matched Zn0.46Cd0.54Se/ZnCdMgSe multiple-quantum-wells (MQWs) have been recognized as very promising materials to fabricate intersubband (ISB) devices such as quantum cascade lasers and mid-infrared photoconductors. These structures have important applications in biological and chemical detections. The ISB transition covers a wide mid-infrared wavelength range from 1.3 μm to a few tens of μm.In this work, two heavily doped n-Zn0.46Cd0.54Se/Zn0.24Cd0.25Mg0.51Se MQW structures have been grown on InP (001) substrate by molecular beam epitaxy. Temperature dependent steady-state photoluminescence (SSPL), temperature dependent time- resolved photoluminescence (TRPL), and Fourier transform infrared spectroscopy (FTIR) were performed to characterize their interband and ISB properties. These two MQW samples have similar structures except different well widths and different number of periods. The integrated SSPL intensities and the PL decay times of the MQWs were measured as functions of temperature in the range from 77 K to 290 K. The luminescence efficiency of the sample with 28 Å well width is larger than that of the sample with 42 Å well width although both samples exhibit similar temperature dependence of PL intensity. Time-resolved PL measurements show that the PL decay times of both samples decrease with increasing temperature. From 77 K to 290 K, the decay time of the sample with 28 Å well width is in the range of 440 ps ∼ 120 ps and is much longer than that of the sample with 42 Å well width, which is in the range of 65 ps ∼ 25 ps. Strong non-radiative recombinations dominate the luminescence behavior of the wider MQWs. Intersubband absorption spectra of the samples were measured by FTIR and show peak absorption at wavelengths of 3.99 μm and 5.35 μm for the MQWs with well widths of 28 Å and 42 Å, respectively, falling within the 3-5 Åm range, which is of great interest for the infrared photodetector applications.

Influence of Er depth profiles on luminescence properties of Er-doped GaN

2000 ◽  
Vol 639 ◽  
Author(s):  
Shin-ichiro Uekusa ◽  
Tomoaki Hirano
Keyword(s):  
Room Temperature ◽  
Thermal Quenching ◽  
Nonradiative Recombination ◽  
Temperature Dependent ◽  
Depth Profiles ◽  
First Excited State ◽  
Quenching Process ◽  
Er Doped ◽  
Auger Effect ◽  
Temperature Dependent Photoluminescence

ABSTRACTErbium (Er) ions were implanted into gallium nitride (GaN) and the temperature-dependent photoluminescence (PL) and PL lifetime were characterized. Thermal quenching of the Er3+ luminescence was restrained by using GaN as a host material and PL was observed from Er3+ at room temperature. We prepared a flat depth profile of the density distribution of Er by ion-implanted into GaN and monitored the thermal quenching process due to the residual defects after implantation and annealing. We also monitored the auger effect that is believed to be the main cause of the thermal quenching process and concluded that, in the temperature range 15 K to 100 K, the thermal quenching process is dominated by nonradiative recombination from the first excited state (4I13/2) to the ground state (4I15/2) of Er3+.

scholarly journals Minority Carrier Lifetime Measurements on 4H-SiC Epiwafers by Time-Resolved Photoluminescence and Microwave Detected Photoconductivity

2019 ◽  
Vol 963 ◽  
pp. 313-317
Author(s):  
Jan Beyer ◽  
Nadine Schüler ◽  
Jürgen Erlekampf ◽  
Birgit Kallinger ◽  
Patrick Berwian ◽  
...  
Keyword(s):  
Room Temperature ◽  
Carrier Lifetime ◽  
Minority Carrier ◽  
Minority Carrier Lifetime ◽  
Temperature Dependent ◽  
Lifetime Measurements ◽  
Time Resolved ◽  
Excess Carrier ◽  
Time Resolved Photoluminescence ◽  
Different Thickness

Temperature dependent microwave detected photoconductivity MDP and time-resolved photoluminescence TRPL were employed to investigate the carrier lifetime in CVD grown 4H-SiC epilayers of different thickness. The minority carrier lifetime may be found from both theMDP and defect PL decay at room temperature for all epilayers, whereas the near bandedge emission (NBE) decay is much faster for thin epilayers (<17 μm) due to the substrate proximity and only follows the minority carrier lifetime for thicker samples at lower excess carrier concentrations.

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