Articles de revues : « SiGe, quantum well, photoluminescence, carrier dynamics »

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Lee, Zhen Sheng, Ling Min Kong, Zhe Chuan Feng, Gang Li, Hung Lin Tsai et Jer Ren Yang. « Luminescence Dynamics and Structural Investigation of InGaN/GaN Multiple Quantum Well Light Emitting Diodes ». Advanced Materials Research 216 (mars 2011) : 445–49. http://dx.doi.org/10.4028/www.scientific.net/amr.216.445.

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Luminescence properties of blue emission InGaN/GaN multiple quantum well (MQW) have been studied by temperature dependent photoluminescence (PL), photoluminescence excitation (PLE) and time-resolved photoluminescence (TRPL) spectroscopic techniques. Two typical samples are studied, both consisting of five periods of InGaN wells with different indium compositions of 21% and 24%, respectively. According to the PL and PLE measurement results, large values of activation energy and Stokes’ shift are obtained. This indicates that higher Indium composition results in an increase of composition fluctuation in the InGaN MQW region, showing the stronger carrier localization effect. The lifetime at the low-energy side of the InGaN peaks is longer for higher indium composition, as expected from the larger Stokes shift.

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Ng, T. K., S. F. Yoon, S. Z. Wang, L. H. Lin, Y. Ochiai et T. Matsusue. « Photoluminescence characterization of GaInNAs/GaAs quantum well carrier dynamics ». Journal of Applied Physics 94, n^o 5 (septembre 2003) : 3110–14. http://dx.doi.org/10.1063/1.1601297.

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Hung, K. M., J. Y. Kuo, C. C. Hong, H. H. Cheng, G. Sun et R. A. Soref. « Carrier dynamics of terahertz emission based on strained SiGe/Si single quantum well ». Applied Physics Letters 96, n^o 21 (24 mai 2010) : 213502. http://dx.doi.org/10.1063/1.3432075.

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WENG, GUO-EN, BAO-PING ZHANG, MING-MING LIANG, XUE-QIN LV, JIANG-YONG ZHANG, LEI-YING YING, ZHI REN QIU et al. « OPTICAL PROPERTIES AND CARRIER DYNAMICS IN ASYMMETRIC COUPLED InGaN MULTIPLE QUANTUM WELLS ». Functional Materials Letters 06, n^o 02 (avril 2013) : 1350021. http://dx.doi.org/10.1142/s1793604713500215.

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Optical properties and carrier dynamics of InGaN/GaN asymmetric coupled quantum wells (ACQWs) are studied by excitation-power-dependent photoluminescence (PL), photoreflectance (PR) and time-resolved PL (TRPL) experiments. Under weak excitations, only the emission from the widest well is observed due to the tunneling from narrower to wider wells. Under strong excitations, the carrier distribution becomes more uniform and an enhanced emission from the mid well (2.5 nm well) is observed. Dependence of the PL intensity on excitation power is well explained by a rate equation model. The energy levels in the ACQW structure are clearly revealed by PR measurements and are in good agreement with calculations. Our results indicate that the enhanced emission from the mid well is ascribed to "reverse tunneling" from 3.0 to 2.5 nm well, which is confirmed by TRPL experiments.

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KOCHERESHKO, V. P., A. V. PLATONOV, G. V. MIKHAILOV, J. PULS, F. HENNEBERGER, D. R. YAKOVLEV et W. FASCHINGER. « TEMPORAL DYNAMICS OF EXCITON–TRION SYSTEM ». International Journal of Nanoscience 02, n^o 06 (décembre 2003) : 453–59. http://dx.doi.org/10.1142/s0219581x03001553.

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Time-resolved and time-integrated circularly-polarized photoluminescence of excitons and trions have been studied in external magnetic fields up to 10 T. ZnSe-based quantum well structures of n-type with carrier densities varied from 5×109 to 1011 cm -2 were used in this study. Absence of the chemical equilibrium in the exciton–trion system has been demonstrated at low temperatures (<10 K ). The recovery of the equilibrium has been found at elevated temperatures (<15 K ).

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Lockwood, D. J., N. L. Rowell, A. Benkouider, A. Ronda, L. Favre et I. Berbezier. « Bright photoluminescence from ordered arrays of SiGe nanowires grown on Si(111) ». Beilstein Journal of Nanotechnology 5 (30 décembre 2014) : 2498–504. http://dx.doi.org/10.3762/bjnano.5.259.

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We report on the optical properties of SiGe nanowires (NWs) grown by molecular beam epitaxy (MBE) in ordered arrays on SiO2/Si(111) substrates. The production method employs Au catalysts with self-limited sizes deposited in SiO2-free sites opened-up in the substrate by focused ion beam patterning for the preferential nucleation and growth of these well-organized NWs. The NWs thus produced have a diameter of 200 nm, a length of 200 nm, and a Ge concentration x = 0.15. Their photoluminescence (PL) spectra were measured at low temperatures (from 6 to 25 K) with excitation at 405 and 458 nm. There are four major features in the energy range of interest (980–1120 meV) at energies of 1040.7, 1082.8, 1092.5, and 1098.5 meV, which are assigned to the NW-transverse optic (TO) Si–Si mode, NW-transverse acoustic (TA), Si–substrate–TO and NW-no-phonon (NP) lines, respectively. From these results the NW TA and TO phonon energies are found to be 15.7 and 57.8 meV, respectively, which agree very well with the values expected for bulk Si1− x Ge x with x = 0.15, while the measured NW NP energy of 1099 meV would indicate a bulk-like Ge concentration of x = 0.14. Both of these concentrations values, as determined from PL, are in agreement with the target value. The NWs are too large in diameter for a quantum confinement induced energy shift in the band gap. Nevertheless, NW PL is readily observed, indicating that efficient carrier recombination is occurring within the NWs.

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Güçlü, A. D., C. Rejeb, R. Maciejko, D. Morris et A. Champagne. « Photoluminescence study of carrier dynamics and recombination in a strained InGaAsP/InP multiple-quantum-well structure ». Journal of Applied Physics 86, n^o 6 (15 septembre 1999) : 3391–97. http://dx.doi.org/10.1063/1.371219.

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Chi, Haitao, Yu Du et Gongyu Li. « Analysis of InGaN Multiple-Quantum-Well Photoelectric Device of Visible Light Communication ». Journal of Nanoelectronics and Optoelectronics 15, n^o 7 (1 juillet 2020) : 909–16. http://dx.doi.org/10.1166/jno.2020.2850.

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The key to achieving high-speed and high-quality visible light communication is to increase the modulation speed of Light-Emitting Diode (LED). Therefore, in this study, the influence of the Composite Mechanism of Carrier (CMC) on the modulation speed of LED is studied by designing different structures of the InGaN Multi-quantum-well (MQW) LED active region. Because the carrier subspace waves function of narrow quantum well LED overlaps more frequently and the electron leakage effect is more significant, the compound rate is faster and the modulation bandwidth is higher. InGaN quantum barrier LED with a content of 1% can increase the weight of radiation recombination, which makes the modulation bandwidth higher than GaN quantum barrier LEDs; when the in content is 5%, electron leakage and Auger recombination have a dominant position. Moreover, because these two compounding mechanisms have a fast compounding rate, the modulation bandwidth is significantly increased. Then the 405 nm laser-excited photoluminescence (PL) is introduced to analyze the carrier dynamics in the LED and obtain the related processes of carrier distribution and transport. The proposed carrier microscopic model can well explain change characteristics of the PL luminescence peak, luminous intensity, and half-height width of InGaN/GaN MQW LED with different excitation wavelengths. At low temperature, the PL peak of the InGaN/GaN quantum well LED redshifts with the increase of temperature, because the weakly bound carrier transfers the obtained energy to the deeply bound energy level of high In content.

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Li, Jianfei, Duo Chen, Kuilong Li, Qiang Wang, Mengyao Shi, Chen Cheng et Jiancai Leng. « Carrier Dynamics in InGaN/GaN-Based Green LED under Different Excitation Sources ». Crystals 11, n^o 9 (2 septembre 2021) : 1061. http://dx.doi.org/10.3390/cryst11091061.

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The excitation power and temperature dependence of the photoluminescence (PL) and electroluminescence (EL) spectra were studied in green InGaN/GaN multiple quantum well (MQW)-based light-emitting diodes (LED). An examination of the PL-325, PL-405, and EL spectra at identical optical or electrical generation rates at room temperature showed that the normalized spectra exhibited different characteristic peaks. In addition, the temperature behavior of the peak energy was S-shaped for the PL-405 spectrum, while it was V-shaped for the EL spectrum. These measurement results demonstrate that the excitation source can affect the carrier dynamics about the generation (injection), transfer, and distribution of carriers.

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Jang, D. J., J. T. Olesberg, M. E. Flatté, Thomas F. Boggess et T. C. Hasenberg. « Hot carrier dynamics in a (GaInSb/InAs)/GaInAlAsSb superlattice multiple quantum well measured with mid-wave infrared, subpicosecond photoluminescence upconversion ». Applied Physics Letters 70, n^o 9 (3 mars 1997) : 1125–27. http://dx.doi.org/10.1063/1.118504.

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Schrottke, L., R. Hey et H. T. Grahn. « Population properties and carrier dynamics in a GaAs/(Al,Ga)As double-quantum-well superlattice investigated by time-resolved photoluminescence spectroscopy ». Applied Physics Letters 79, n^o 5 (30 juillet 2001) : 629–31. http://dx.doi.org/10.1063/1.1388873.

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Marcinkevičius, Saulius, Rosa Leon, Charlene Lobo, Brian Magness et William Taylor. « Time Resolved Studies of Proton Irradiated Quantum Dots ». MRS Proceedings 722 (2002). http://dx.doi.org/10.1557/proc-722-k11.6.

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AbstractThe effects of proton irradiation on carrier dynamics were measured by time-resolved photoluminescence on InGaAs/GaAs quantum dot structures with different dot density and substrate orientation, as well as on InAlAs/AlGaAs quantum dots. Results were compared to irradiation effects on carrier dynamics in thin InGaAs quantum wells. We find that carrier lifetimes in QDs are much less affected by proton irradiation than in quantum wells, which can be attributed to the three-dimensional carrier confinement in quantum dots.

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Vial, J.-C., B. Pépin-Donat, A. Viallat et P. Fedorko. « Carrier Dynamics in Poly(Octylthiophene) Gels ». MRS Proceedings 660 (2000). http://dx.doi.org/10.1557/proc-660-jj8.22.

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ABSTRACTCarrier dynamics properties in swollen poly(octylthiophene) gels are investigated via their radiative and non-radiative recombination rates (Wr and Wnr respectively) as a function of their swelling ratio (Q). Photoluminescence decay time (τ, in the picosecond range) and luminescence quantum efficiency (QE) are found to strongly increase with Q. This implies that Wr increases and Wnr decreases as Q increases; such a result cannot be understood if one accounts only for the well-known dilution effect observed for organic dyes. Our interpretation is that the enhanced carrier transport due to the increase of interchain interactions observed upon deswelling induces a separation of carriers. Then, these latter present an increased probability to find non-radiative traps. Variation of the conductivity versus Q in doped gels is also discussed.

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Beyer, A., E. Müller, H. Sigg, S. Stutz, C. David, D. Grützmacher et K. Ensslin. « Optical and structural analysis of Ge quantum dots embedded in strained Si quantum wells grown on patterned substrates ». MRS Proceedings 638 (2000). http://dx.doi.org/10.1557/proc-638-f14.8.1.

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AbstractGermanium quantum dots embedded in silicon have been used in the past to improve the opto-electronic properties of Si based materials. The idea is to overcome the limitation of the indirect band gap of Si by a strong localization of the carriers in quantum dots. However, the Ge quantum dots provide a strong carrier confinement only for the holes, the electrons are only weakly confined in the Si. In this study we embedded the Ge quantum dots in strained Si quantum wells grown on relaxed SiGe buffer layers. The strained Si quantum wells provide a confinement of the electrons in the vicinity of the Ge dots.The structures were deposited on planar as well as on patterned substrates by molecular beam epitaxy. The structural and optical properties of the samples were analyzed using high resolution cross sectional transmission electron microscopy (TEM) as well as low temperature photoluminescence. The size of the mesa structures have been used as experimental parameter. Relaxed buffer layers grown on line shaped mesa structures show a strongly reduced dislocation density. Consequently the deep luminescence attributed to dislocations in the buffer layers is strongly reduced and pronounced photoluminescence of the quantum structures grown on top of the buffer layers can be observed.

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Cartwright, A. N., Paul M. Sweeney, Thomas Prunty, David P. Bour et Michael Kneissl. « Electric Field Distribution in strained p-i-n GaN/InGaN multiple quantum well structures. » MRS Internet Journal of Nitride Semiconductor Research 4, n^o 1 (1999). http://dx.doi.org/10.1557/s1092578300000685.

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The presence of piezoelectric fields within p-i-n GaN/InGaN multiple quantum well structures is discussed. Time integrated and time-resolved photoluminescence measurements and theoretical calculations of the effect of these fields is presented. Furthermore, a description of how these fields influence the carrier dynamics and a discussion of how the piezoelectric field effects the design of GaN/InGaN devices is presented.

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Cartwright, Alexander N., M. C.-K. Cheung, F. Shahedipour-Sandvik, J. R. Grandusky, M. Jamil, V. Jindal, S. B. Schujman et al. « Ultrafast Carrier Dynamics and Recombination in Green Emitting InGaN MQW LED ». MRS Proceedings 916 (2006). http://dx.doi.org/10.1557/proc-0916-dd04-10.

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AbstractTime-resolved photoluminescence studies can provide useful information for the development of InGaN/GaN heterostructures for long wavelength visible emitters. In this paper, we present results of time-resolved photoluminescence from samples grown using two different approaches to achieve green emission from InGaN/GaN MQWs. In one approach, samples, with high indium incorporation, were grown on a high quality AlN substrate to achieve green emission. The resulting photoluminescence decay of the green luminescence is long-lived and non-exponential. Quantitative analysis showed that the decay has a stretched-exponential characteristic, typical of InGaN/GaN MQW with potential fluctuation along the growth plane. This carrier localization, in a structure with low defect density, proves to be an effective means to achieve green emission. In another approach, a piezoelectric Stark-like ladder effect is used. In this case, a methodical layer-by-layer growth homogeneity optimization process was adopted to achieve an optical transition below the electron to heavy-hole (e1hh1) transition when the quantum well is subjected to the strong piezoelectric polarization dipole. This approach has proven to be successful in achieving green luminescence on conventional sapphire substrates. The resulting photoluminescence decay at 14 K, of a sample grown by this approach, is single exponential and shorter in duration than the decay observed in the first approach. This exponential decay is consistent with previous AFM studies that revealed a homogeneous active region.

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Lefebvre, P., J. Allègre, B. Gil, A. Kavokine, H. Mathieu, W. Kim, A. Salvador, A. Botchkarev et H. Morkoç. « Time-Resolved Photoluminescence of GaN / Ga0.93Al0 .07N Quantum Wells ». MRS Proceedings 482 (1997). http://dx.doi.org/10.1557/proc-482-607.

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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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Brübach, J., J. E. M. Haverkort, J. H. Wolter, P. D. Wang, N. N. Ledentsov et C. M. Sotomayor Torres. « Exciton Dynamics in Ultrathin InAs/GaAs Quantum-Wells ». MRS Proceedings 406 (1995). http://dx.doi.org/10.1557/proc-406-283.

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AbstractWe have studied the transient behaviour of a sharp emission line, which emerges close to the heavy-hole (hh) exciton photoluminescence line in a 1.6 monolayer thick InAs layer embedded in a GaAs matrix, when the light-hole (lh) exciton transition is excited. We find, that the decaytime of the sharp line is equal to the lh-exciton lifetime for excitation on resonance, but it strongly decreases for excitation off resonance. Since in our structure the energy separation between the hhand lh-exciton transitions amount to one GaAs LO phonon we conclude, that the sharp line originates from double resonant Raman scattering for off resonant excitation, whereas it is predominantly due to resonant luminescence for excitation on resonance. The strong decrease of the intensity of the sharp line due to a temperature rise from 4 to 18K proves the existence of a well confined lh-exciton state. In addition, we performed carrier capture measurements on this structure. We find a constant capture time of 20ps at the lh-exciton transition, whereas the capture time decreases step-like from 55ps to 22ps within the hh-exciton transition. This provides clear evidence for a two-step capture process, where the lh-level acts as an intermediate capture state.

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Morel, Aurelien, Pierre Lefebvre, Thierry Taliercio, Bernard Gil, Nicolas Grandjean, Benjamin Damilano et Jean Massies. « Microscopic Description of Radiative Recombinations in InGaN/GaN Quantum Systems ». MRS Proceedings 743 (2002). http://dx.doi.org/10.1557/proc-743-l5.5.

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ABSTRACTRecombination dynamics in a variety of InGaN/GaN quantum systems has been studied by time resolved photoluminescence (PL). We have discovered that the time-decay of PL exhibits a scaling law: the nonexponential shape of this decay is preserved for quantum wells and quantum boxes of various sizes while their decay time varies over several orders of magnitude. To explain these results, we propose an original model for electron-hole pair recombination in these systems, combining the effects of internal electric fields and of carrier localization on a nanometer-scale. These two intricate effects imply a separate localization of electrons and holes. Such a microscopic description accounts very well for both the decays shape and the scaling law.

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Khee, Ng Tien, Yoon Soon Fatt et Fan Weijun. « Analysis of Photoluminescence Efficiency of Annealed GaInNAs Quantum Well Grown by Solid Source Molecular Beam Epitaxy ». MRS Proceedings 799 (2003). http://dx.doi.org/10.1557/proc-799-z5.14.

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ABSTRACTThe carrier dynamics of a 7.5 nm GaInNAs quantum well (QW) are studied by photoluminescence (PL) at a low temperature regime of 4 K to 150 K. The PL emission efficiency of the QW is initially evaluated to examine the recombination mechanisms in the QW. A dual-activation-energy model is later found to fit the integrated PL intensity vs. temperature curve better than a single-activation-energy model. The two states that correspond to the above activation energies could have resulted in a much faster PL intensity quenching in the GaInNAs QW as compared to that of a reference GaInAs QW. One of the states is identified as a localized state that traps carriers at a low temperature range of less than ∼100 K. The other state has a larger quenching effect at temperatures higher than 100 K and this state is not studied in this paper. By fitting the original PL spectra with two Gaussian functions, the temperature dependent PL integrated intensity of both Gaussian functions was also studied to further characterize the GaInNAs QW. The analysis gives evidence of the localization behaviour in this QW.

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Chen, Fei, A. N. Cartwright, Paul M. Sweeney, M. C. Cheung, Jeffrey S. Flynn et David Keogh. « Influence of growth temperature on emission efficiency of InGaN/GaN multiple quantum wells ». MRS Proceedings 693 (2001). http://dx.doi.org/10.1557/proc-693-i6.27.1.

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AbstractA comparative study, using time-resolved and CW photoluminescence spectroscopy, of MOVPE grown InGaN/GaN multiple quantum wells deposited on HVPE GaN/Sapphire at different growth temperatures was undertaken. It was found that the PL linewidth increased and the peak emission energy decreased as the growth temperature was reduced. Moreover, the sample grown at an intermediate growth temperature exhibited total integrated luminescence intensity much greater than the samples grown at higher or lower growth temperatures. A phenomenological carrier recombination dynamics model based on the competition of quantum well-like radative recombination, spatially localized radiative recombination in potential minima and non-radiative recombination through defects is presented to provide an explanation of the observed emission dynamics and efficiency. In this model, the emission efficiency is determined by the relative area of defects and the number density of localized states in the potential minima, both of which are influenced by the growth temperature. Furthermore, the photon energy dependent lifetimes are well fitted with this model by assuming a Gaussian shape localized states distribution. The localized potential minima are consistent with nanoscale indium rich regions due to indium aggregation.

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Tanaka, Shiki, Ryota Ishii, Norman Susilo, Tim Wernicke, Michael Kneissl, Mitsuru FUNATO et Yoichi KAWAKAMI. « Picosecond-laser-excited photoluminescence study of AlGaN quantum wells on epitaxially laterally overgrown AlN/sapphire under selective and non-selective excitation conditions ». Japanese Journal of Applied Physics, 26 septembre 2022. http://dx.doi.org/10.35848/1347-4065/ac94fd.

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Abstract The radiative recombination efficiency (RRE) of AlGaN quantum wells on epitaxially laterally overgrown AlN/sapphire templates was investigated by picosecond-laser-excited photoluminescence (PL) spectroscopy under selective and non-selective excitation conditions. The PL efficiency, which was deduced by excitation-power-dependent PL measurements at low temperature (LT) and room temperature (RT), was unity at LT under both excitation conditions; However, at RT, the PL efficiency under non-selective excitation conditions was lower than that under selective excitation conditions. Time-resolved PL measurements revealed that, under non-selective excitation conditions, additional carriers are provided from the surrounding layers to the quantum-well layers, especially at LT. Therefore, at RT, the PL efficiency does not correspond to the RRE under non-selective excitation conditions. We propose a model to explain carrier dynamics under the two excitation conditions showing that the PL efficiency equals the RRE under selective excitation conditions.

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Gholami, M., M. Esmaeili, H. Haratizadeh, P. Holtz et M. Hammar. « Evaluation of optical quality and properties of Ga0.64In0.36N0.006As0.994 lattice matched to GaAs by using photoluminescence spectroscopy ». Opto-Electronics Review 17, n^o 3 (1 janvier 2009). http://dx.doi.org/10.2478/s11772-009-0008-9.

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AbstractWe have investigated optical properties of Ga0.64In0.36N0.006As0.994/GaAs single quantum-well structures using photoluminescence technique. We have found that nitrogen creates potential fluctuations in the InGaNAs structures, so it is the cause of trap centres in these structures and leads to localized excitons recombination dynamics. The near-band edge PL at 2 K exhibited a blueshift with an increase in excitation intensity of a sample but there is not such a shift in the PL peak position energy of same sample at 150 K. It has been found that PL spectra have a large full width at half maximum (FWHM) value at 2 K. These results are discussed in terms of carrier localization. Additionally, our results suggest decreasing PL integrated intensity in this structure, possibly due to non-radiative recombination. It has been shown that thermal annealing reduces the local strain created by nitrogen. By annealing process, a blue shifted emission can be observed.

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Nag, Dhiman, S. Bhunia, Ritam Sarkar, Soumyadip Chatterjee et Apurba Laha. « Investigating defects in InGaN based optoelectronics : from material and device perspective ». Materials Research Express, 30 janvier 2023. http://dx.doi.org/10.1088/2053-1591/acb759.

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Abstract III-nitride optoelectronics have revolutionized solid-state lighting technology. However, non-radiative defects play a major bottleneck in determining the performance of InGaN-based optoelectronics devices. It becomes especially challenging when high indium is required to be incorporated to obtain emission at higher wavelength (>500 nm). In this review article, we are going to discuss our investigation on the origin of defects in InGaN-based optoelectronics devices from the material and device perspective and characterize them through various techniques. This article broadly consists of two parts. In the first part, we investigate defects in InGaN based optoelectronics from a material point of view. Here, we discuss the challenges in the growth of InGaN planar (2-dimensional) and nanowires (1-dimensional) with high indium (≥20%) incorporation using the plasma-assisted molecular beam epitaxy (PA-MBE) technique. Photoluminescence spectroscopy (PL) has been performed to characterize these grown samples to assess their optical quality. Atomic force microscopy (AFM) has been employed to characterize the surface morphology of grown InGaN layers. High-resolution transmission electron microscopy (HRTEM) and scanning electron microcopy (SEM) are also used to characterize InGaN planar and nanowire samples grown under various process conditions. In the second part, we investigate the role of defects on InGaN optoelectronics from a device point of view. Here, we discuss the fabrication of InGaN multi-quantum well-based light emitting diodes (LEDs). Temperature-dependent current vs. voltage measurements are carried out to investigate the role of defects on carrier dynamics under forward and reverse bias conditions. Frequency-dependent capacitance vs. voltage (CV) and conductance vs. voltage (GV) techniques are employed extensively to characterize defects in fabricated InGaN LEDs.

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