Journal articles: 'QWs'

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Žurauskienė, N., S. Ašmontas, A. Dargys, J. Kundrotas, G. Janssen, E. Goovaerts, Stanislovas Marcinkevičius, Paul M. Koenraad, J. H. Wolter, and R. P. Leon. "Semiconductor Nanostructures for Infrared Applications." Solid State Phenomena 99-100 (July 2004): 99–108. http://dx.doi.org/10.4028/www.scientific.net/ssp.99-100.99.

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We present the results of time-resolved photoluminescence (TRPL) and optically detected microwave resonance (ODMR) spectroscopy investigations of semiconductor quantum dots and quantum wells. The ODMR spectra of InAs/GaAs QDs were detected via modulation of the total intensity of the QDs emission induced by 95 GHz microwave excitation and exciton fine structure was studied. Very long life times (up to 10 ns) of photoexcited carriers were observed in this system using TRPL at low temperatures and excitation intensities promising higher responsitivity of such QDs for quantum dot infrared photodetector development. The effects of proton and alpha particles irradiation on carrier dynamics were investigated on different InGaAs/GaAs, InAlAs/AlGaAs and GaAs/AlGaAs QD and QW systems. The obtained results demonstrated that carrier lifetimes in the QDs are much less affected by proton irradiation than that in QWs. A strong influence of irradiation on the PL intensity was observed in multiple QWs after high-energy alpha particles irradiation.

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Kawazu, Takuya. "Valence Band Mixing in GaAs/AlGaAs Quantum Wells Adjacent to Self-Assembled InAlAs Antidots." Journal of Nanomaterials 2019 (April 28, 2019): 1–7. http://dx.doi.org/10.1155/2019/5349291.

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Optical properties of GaAs/AlGaAs quantum wells (QWs) in the vicinity of InAlAs quantum dots (QDs) were studied and compared with a theoretical model to clarify how the QD strain affects the electronic states in the nearby QW. In0.4Al0.6As QDs are embedded at the top of the QWs; the QD layer acts as a source of strain as well as an energy barrier. Photoluminescence excitation (PLE) measurements showed that the QD formation leads to the increase in the ratio Ie-lh/Ie-hh of the PLE intensities for the light hole (lh) and the heavy hole (hh), indicating the presence of the valence band mixing. We also theoretically calculated the hh-lh mixing in the QW due to the nearby QD strain and evaluated the PLE ratio Ie-lh/Ie-hh.

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Yunovich, A. E., V. E. Kudryashov, A. N. Turkin, A. N. Kovalev, and F. I. Manyakhin. "Electroluminescence Properties of InGaN/AlGaN/GaN Light Emitting Diodes with Quantum Wells." MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 659–64. http://dx.doi.org/10.1557/s1092578300003215.

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Electroluminescence spectra of light-emitting diodes based on InGaN/AlGaN/GaN heterostructures with single and multiple quantum wells (QWs) are analyzed by models of radiative recombination in 2D-structures with band tails. Equations of the model fit spectra quite good in a wide range of currents. Parameters of the fit are discussed and compared for single and multiple QWs. Tunnel effects play a sufficient role in blue LEDs with single QWs at low currents; they can be neglected in LEDs with multiple QWs. A new spectral band was detected at the high energy side of the spectra of green LEDs with multiple QWs; it is attributed with large scale inhomogenities of In distribution in InGaN QWs.*)

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Wysham, Carol H., Julio Rosenstock, Marion L. Vetter, Hui Wang, Elise Hardy, and Nayyar Iqbal. "Further improvement in glycemic control after switching from exenatide two times per day to exenatide once-weekly autoinjected suspension in patients with type 2 diabetes: 52-week results from the DURATION-NEO-1 study." BMJ Open Diabetes Research & Care 8, no. 1 (October 2020): e000773. http://dx.doi.org/10.1136/bmjdrc-2019-000773.

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IntroductionInvestigate the effects of switching from two times per day exenatide to once-weekly exenatide administered by autoinjector (exenatide once-weekly suspension by autoinjector (QWS-AI)) or treatment with exenatide QWS-AI for 1 year.Research design and methodsIn this phase III open-label study, adults with type 2 diabetes were randomized to receive exenatide QWS-AI (2 mg) or exenatide two times per day (5 mcg for 4 weeks, followed by 10 mcg) for 28 weeks. During a subsequent non-randomized 24-week extension, patients who received exenatide two times per day were switched to exenatide QWS-AI and those randomized to exenatide QWS-AI continued this treatment. Efficacy measures included changes from baseline in glycated hemoglobin (A1C), fasting plasma glucose (FPG), and body weight.ResultsIn total, 315 patients (mean baseline A1C of 8.5%) completed the initial 28 weeks of randomized treatment with exenatide QWS-AI (n=197) or exenatide two times per day (n=118) and were included in the 24-week extension (mean A1C of 7.0% and 7.3%, respectively, at week 28). From weeks 28–52, patients who switched from exenatide two times per day to exenatide QWS-AI had additional A1C reductions of approximately 0.5% (mean A1C change from baseline of –1.4% at week 52) and further reductions from baseline in FPG. Patients who continued exenatide QWS-AI treatment for 52 weeks showed clinically relevant A1C reductions (mean A1C change from baseline of –1.3% at week 52). Body-weight reductions achieved through week 28 were sustained at week 52 in both groups. There were no unexpected safety concerns or changes in the safety profile among patients who switched from exenatide two times per day to exenatide QWS-AI or those who continued exenatide QWS-AI treatment for 52 weeks.ConclusionsSwitching from exenatide two times per day to exenatide QWS-AI resulted in further A1C reductions and maintenance of earlier decreases in body weight, while continued therapy with exenatide QWS-AI for 52 weeks maintained A1C and body-weight reductions, without additional safety or tolerability concerns.Trial registration numberNCT01652716.

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Santiago, Svette Reina Merden, Septem P. Caigas, Tzu-Neng Lin, Chi-Tsu Yuan, Ji-Lin Shen, Ching-Hsueh Chiu, and Hao-Chung Kuo. "Tunnel injection from WS2 quantum dots to InGaN/GaN quantum wells." RSC Advances 8, no. 28 (2018): 15399–404. http://dx.doi.org/10.1039/c7ra13108a.

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In this manuscript, an effective tunnel-injection structure, in which the WS₂ quantum dots (QDs) act as the electron injector and the InGaN quantum wells (QWs) act as the light emitters, separated by GaN barriers.

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Минтаиров, С. А., Н. А. Калюжный, А. М. Надточий, М. В. Максимов, В. Н. Неведомский, Л. А. Сокура, С. С. Рувимов, М. З. Шварц, and А. Е. Жуков. "Многослойные InGaAs-гетероструктуры "квантовая яма-точки" в фотопреобразователях на основе GaAs." Физика и техника полупроводников 52, no. 10 (2018): 1131. http://dx.doi.org/10.21883/ftp.2018.10.46452.8879.

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AbstractGaAs photovoltaic converters containing quantum well-dot (QWD) heterostructures are studied. The QWD properties are intermediate between those of quantum wells (QWs) and quantum dots. The QWDs are obtained by the epitaxial deposition of In_0 . 4Ga_0 . 6As with a nominal thickness of 8 single layers by metal-organic vapor phase epitaxy. QWDs are a dense array of elastically strained islands that localize carriers in three directions and are formed by a local increase in the indium concentration and/ or InGaAs-layer thickness. There are two quantum-well levels of varied nature in structures with QWDs. These levels are manifested in the spectral characteristics of GaAs photovoltaic converters. A short-wavelength peak with a maximum at around 935 nm is associated with absorption in the residual QW, and the long-wavelength peak (1015–1030 nm) is due to absorption in the QWDs. Investigation by transmission electron microscopy demonstrates that an increase in the number of InGaAs layers leads to stronger elastic stresses, which, in turn, increases the carrier confinement energy in the QWDs and lead to a corresponding long-wavelength shift of the internal quantum efficiency spectrum.

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Chen, Ping, Young Jae Park, Yuh-Shiuan Liu, Theeradetch Detchprohm, P. Douglas Yoder, Shyh-Chiang Shen, and Russell D. Dupuis. "Epitaxial Growth and Optically Pumped Stimulated Emission in AlGaN/InGaN Ultraviolet Multi-Quantum-Well Structures." Journal of Electronic Materials 49, no. 4 (January 8, 2020): 2326–31. http://dx.doi.org/10.1007/s11664-019-07932-x.

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AbstractThe thermal effect of the growth temperature on interface morphology and stimulated emission in ultraviolet AlGaN/InGaN multiple quantum wells (MQWs) are experimentally investigated. During the MOCVD epitaxial growth of AlGaN/InGaN MQWs, the ramping rate from a lower temperature for InGaN quantum wells (QWs) to a higher one for AlGaN quantum barriers (QBs) is intentionally changed from 1.0°C/s to 4.0°C/s. Atomic force microscopy images show that the surface morphology of InGaN QWs, which is improved by a thermal effect when the growth temperature rises to the set value of the AlGaN QBs, varies with different temperature ramping rates. The results of stimulated emission indicate that the threshold pumping power density of MQWs is decreased with increasing temperature ramping rate from 1.0°C/s to 3.0°C/s and then slightly increased when the ramping rate is 4.0°C/s. This phenomenon is believed to result from the thermal degradation effect during the temperature ramp step. A long-time high-temperature annealing will reduce the density of indium-rich microstructures as well as the corresponding localized state density, which is assumed to contribute to the radiative recombination in the InGaN QWs. Given the great difference between optimal growth temperatures for AlGaN and InGaN layers, a higher ramping rate would be more appropriate for the growth of ultraviolet AlGaN/InGaN MQWs.

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Funato, Mitsuru, and Yoichi Kawakami. "Semipolar III Nitride Semiconductors: Crystal Growth, Device Fabrication, and Optical Anisotropy." MRS Bulletin 34, no. 5 (May 2009): 334–40. http://dx.doi.org/10.1557/mrs2009.96.

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AbstractSemipolar InGaN/GaN quantum wells (QWs) are quite attractive as visible light emitters. One of the reasons is that a better optical transition probability is expected because of weaker internal electric fields, compared to conventional polar QWs. In addition, in-plane optical polarization anisotropy, which is absent in conventional QWs, is another relevant property because it affects device design and also may provide a means for novel applications. We revealed that the in-plane optical anisotropy in semipolar QWs switched from one direction perpendicular to the [0001] crystal axis to the perpendicular direction as the In composition increases. This is a property unique to semipolar QWs and enables, for example, to make cavity mirrors of laser diodes by cleavage. In this article, we describe the concept of semipolar planes and fabrication of high-quality epitaxial films for semipolar QWs. Furthermore, we discuss device fabrication and optical polarization anisotropy.

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Danielson, Andrew J. "On the History and Evolution of Qws: The Portrait of a First Millennium BCE Deity Explored through Community Identity." Journal of Ancient Near Eastern Religions 20, no. 2 (April 16, 2021): 113–89. http://dx.doi.org/10.1163/15692124-12341314.

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Abstract This article explores the history and evolution of the deity Qws through a study of the communities affiliated with Qws, presenting also a current collection of all inscriptional references to this deity. Diachronic and spatial analyses of the references reveal nuanced insights into how Qws was understood by his adherents, as well as the patterns of behavior, linguistic practices, and identities that marked these communities. The attestations of Qws demonstrate the deity’s relative obscurity during the Late Bronze Age, a rapid rise in inscriptional popularity among persons associated with the region of Edom during the late Iron Age, and a regional perpetuation of attestation following the dissolution of the Iron Age southern Levantine polities. Furthermore, attestations of Qws among diasporic community’s present insights into the shifting identities and cultic practices of the immigrant communities affiliated with the deity.

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Geng, Zhenduo, and Yuping Wang. "Optical properties in wurtzite InGaN staggered quantum wells." Modern Physics Letters B 29, no. 15 (June 10, 2015): 1550076. http://dx.doi.org/10.1142/s0217984915500761.

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The polarization field effects on exciton states and optical properties are studied theoretically in the wurtzite (WZ) In x Ga 1-x N / In y Ga 1-y N staggered quantum wells (QWs). Numerical results show that the polarization field effects are obvious on the Stark shifts of the exciton binding energy, the oscillator strength and the emission wavelength when the well width and Indium content y increase in the symmetric staggered QWs. However, the influences of In x Ga 1-x N well layer are remarkable on exciton states and optical properties when the Indium concentration y is small in the asymmetric staggered QWs. In addition, the ground state linear optical susceptibility is also investigated in the WZ staggered QWs.

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POLITANO, ANTONIO, and GENNARO CHIARELLO. "COLLECTIVE ELECTRONIC EXCITATIONS IN SYSTEMS EXHIBITING QUANTUM WELL STATES." Surface Review and Letters 16, no. 02 (April 2009): 171–90. http://dx.doi.org/10.1142/s0218625x09012482.

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We present high-resolution electron energy loss spectroscopy (HREELS) measurements on surface plasmon (SP) dispersion in systems exhibiting quantum well states (QWS), i.e. Na / Cu (111), Ag / Cu (111), and Ag / Ni (111). Our results demonstrate that the dominant coefficient of SP dispersion for thin and layer-by-layer Ag films presenting QWS is quadratic even at small q||, in contrast with previous measurements on Ag semi-infinite media and Ag thin films deposited on Si (111). We suggest that this behavior is due to screening effects enhanced by the presence of QWS shifting the position of the centroid of the induced charge less inside the geometrical surface compared with Ag surfaces and Ag / Si (111). For ultrathin Ag films, i.e. two layers, the dispersion was found to be not positive, as theoretically predicted. Annealing of the Ag film caused an enhancement of the free-electron character of the QWS, thus inducing a negative linear term of the dispersion curve of the SP. Moreover, we report the first experimental evidence of chemical interface damping in thin films for K / Ag / Ni (111). As regards Na / Cu (111), we found a different dispersion curve compared with thick Na films, thus confirming the enhanced screening by Na QWS. Results reported here should shed light on the influence of QWS on dynamical screening phenomena in thin films.

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Cao, Bing Qiang, Hao Ming Wei, Xi Lun Hu, and Hai Bo Gong. "Polar and Nonpolar ZnO Nanowire QWs Grown with PLD Using Nanowire Arrays with Tuning Density as Physical Templates." Materials Science Forum 688 (June 2011): 207–12. http://dx.doi.org/10.4028/www.scientific.net/msf.688.207.

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The encountered difficulties that prevent ZnO nanowires from being used as light-emitters are p-type doping and quantum well (QW) integration. The growth of homogenous nanowire quantum wells is usually influenced by the shadowing effect associated with nanowire growth density. In this paper, based on the growth density control of nanowire array, a new two-step pulsed laser deposition (PLD) strategy was demonstrated to grow two kinds of ZnO nanowire QWs, e.g. radial nonpolar QW and axial polar QW. The growth-density control of ZnO nanowires was realised by introducing a wetting layer and adjusting the substrate-target distances. The structural and optical characterizations of these two kinds of nanowire QWs prove that the radial nanowire QWs are more homogenous than axial QWs, which also show better optical properties.

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Tan, Shuxin, Jicai Zhang, Takashi Egawa, and Gang Chen. "Influence of Quantum-Well Number and an AlN Electron Blocking Layer on the Electroluminescence Properties of AlGaN Deep Ultraviolet Light-Emitting Diodes." Applied Sciences 8, no. 12 (November 26, 2018): 2402. http://dx.doi.org/10.3390/app8122402.

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The influence of quantum-well (QW) number on electroluminescence properties was investigated and compared with that of AlN electron blocking layer (EBL) for deep ultraviolet light-emitting diodes (DUV-LEDs). By increasing the QW number, the band emission around 265 nm increased and the parasitic peak around 304 nm was suppressed. From the theoretical calculation, the electron current overflowing to the p-type layer was decreased as the QW number increased under the same injection. Correspondingly, the light output power also increased. The increment of output power from 5 QWs to 10 QWs was less than that from 10 QWs to 40 QWs, which was very different from what has been reported for blue and near-UV LEDs. The parasitic peak was still observed even when the QW number increased to 40. However, it can be suppressed efficiently by 1 nm AlN EBL for LEDs with 5 QWs. The simulation showed that the insertion of a thin EBL increased the barrier height for electron overflow and the electron current in p-type layers decreased significantly. The results contributed to the understanding of behavior of electron overflow in DUV-LEDs.

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Saidi, Hosni, Said Ridene, and Habib Bouchriha. "Hole intersubband transitions in wurtzite and zinc-blende strained AlGaN/GaN quantum wells and its interband interaction dependence." International Journal of Modern Physics B 29, no. 08 (March 30, 2015): 1550054. http://dx.doi.org/10.1142/s021797921550054x.

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Valence intersubband transitions of the wurtzite (WZ) strained AlGaN/GaN quantum wells are examined theoretically and compared with those of the zinc-blende (ZB) ones. In particular, the effect of the interband interaction between conduction (CB) and valence (VB) bands has been taken into account explicitly. We have used the 8-bands k.p model for both WZ and ZB structures to calculate subband energies and wavefunctions of Al 0.3 Ga 0.7 N/GaN quantum wells (QWs). The results indicate that, the prominent transitions for both ZB and WZ QWs were found to be essentially related to the heavy- and light-hole subbands. For the x-polarization, we have shown that it is necessary to take into account explicitly the interband interaction between CB and VB. Finally, we can predict that WZ QWs are more convenient than ZB QWs in most applications involving intersubband transitions, especially for the z-polarized light.

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Li, Zhiwei, Yugang Zeng, Yue Song, Jianwei Zhang, Yinli Zhou, Yongqiang Ning, Li Qin, and Lijun Wang. "Effect of Substrate Misorientation on the Structural and Optical Characteristics of In-Rich InGaAs/GaAsP Quantum Wells." Applied Sciences 11, no. 18 (September 17, 2021): 8639. http://dx.doi.org/10.3390/app11188639.

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InGaAs quantum well (QW) lasers have attracted significant attention owing to their considerable potential for applications in optical communications; however, the relationship between the misorientation of the substrates used to grow InGaAs QWs and the structural and optical properties of QWs is still ambiguous. In this study, In-rich InGaAs/GaAsP single QWs were grown in the same run via metal organic chemical vapor deposition on GaAs (001) substrates misoriented by 0°, 2°, and 15° toward (111). The effects of substrate misorientation on the crystal quality and structural properties of InGaAs/GaAsP were investigated by X-ray diffraction and Raman spectroscopy. The 0° substrate exhibited the least lattice relaxation, and with increasing misorientation, the degree of lattice relaxation increased. The optical properties of the InGaAs/GaAsP QWs were investigated using temperature-dependent photoluminescence. An abnormal S-shaped variation of the peak energy and inverse evolution of the spectral bandwidth were observed at low temperatures for the 2° substrate, caused by the localization potentials due to the In-rich clusters. Surface morphology observations revealed that the growth mode varied with different miscuts. Based on the experimental results obtained in this study, a mechanism elucidating the effect of substrate miscuts on the structural and optical properties of QWs was proposed and verified.

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Иванов, А. А., В. В. Чалдышев, Е. Е. Заварин, А. В. Сахаров, В. В. Лундин, and А. Ф. Цацульников. "Резонансное отражение света оптической решеткой экситонов, сформированной 100 квантовыми ямами InGaN." Физика и техника полупроводников 55, no. 9 (2021): 733. http://dx.doi.org/10.21883/ftp.2021.09.51286.13.

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Optical properties of a structure with a periodic system of 100 InGaN quantum wells (QWs) separated by non-tunneling GaN barriers have been investigated at room temperature. The structure periodicity corresponded to the Bragg diffraction condition at the frequency of the QW excitons. Numerical modeling using transfer matrices gave a quantitatively accurate fit of the experimental results. The model included the resonance response of A, B, and C excitons in QWs and an optical absorption tail in the barriers and buffer layer. We have determined the radiative and non-radiative broadening of the excitons in the InGaN QWs.

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Akbar, Jehan, Muhammad Hanif, Muhammad Azhar Naeem, and Kamran Abid. "AlGaInAs/InP Based Five & Three Quantum Wells Mode Locked Laser Diodes: A Comparative Study." Elektronika ir Elektrotechnika 26, no. 5 (October 27, 2020): 22–27. http://dx.doi.org/10.5755/j01.eie.26.5.26002.

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Comparison of performance of semiconductor mode-locked laser diodes fabricated using AlGaInAs/InP material containing 5 and 3 quantum wells (QWs) inside the active region is reported. The simulations and experimental results show that lasers containing five QWs materials produce larger beam divergence and temporally broader optical pulses. For improvement in the mode-locking of lasers and reducing the far-field pattern, the number of QWs inside the active region was decreased from five to three and a far-field decreasing layer along with a thick spacer layer were introduced in the n-cladding region of epitaxial material. Before growing the material, simulations were carried out to optimise the design. The lower optical confinement factor and higher gain saturation energy of three QWs based mode-locked lasers provide higher average and peak output power, reduced and symmetric far-field pattern, better radio frequency (RF) spectra, shorter optical pulses, and stable optimal mode-locking for a wide range of gain current and saturable absorber reverse voltage.

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Biswas, Dipankar, Tapas Das, Sanjib Kabi, and Subindu Kumar. "Conspicuous Presence of Higher Order Transitions in the Photoluminescence of In_xGa_1-xN/GaN Quantum Wells." Advanced Materials Research 31 (November 2007): 62–64. http://dx.doi.org/10.4028/www.scientific.net/amr.31.62.

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For successive annealing stages the photoluminescence (PL) peaks of InXGa1-XN/GaN quantum wells (QWs) shift initially towards red which is followed by a blue. This phenomenon contradicts the usual monotonic blueshift. We have found that the phenomena can be explained properly only if we consider recombinations from the higher sub-bands to be present in the PL of the InXGa1-XN/GaN QWs, which is not usual. When a strong piezoelectric field exists across a QW, as encountered in InXGa1-XN/GaN QWs, the probability of optical transitions from higher sub-bands of the QW become more probable. In this paper this theory has been established from experimental results.

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Hai, Tran Thi, Nguyen Huyen Tung, and Nguyen Trung Hong. "Effect from Doping of Quantum Wells on Enhancement of The Mobility Limited by One-Interface Roughness Scattering." Communications in Physics 21, no. 3 (September 19, 2011): 211. http://dx.doi.org/10.15625/0868-3166/21/3/170.

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We present a theoretical study of the effect from doping of quantum wells (QWs) on enhancement of the mobility limited by one-interface roughness scattering. Within the variational approach, we introduce the enhancement factor defined by the ratio of the overall mobility in symmetric two-side doped square QWs to that in the asymmetric one-side counterpart under the same doping and interface profiles. The enhancement is fixed by the sample parameters such as well width, sheet carrier density, and correlation length. So, we propose two-side doping as an efficient way to upgrade the quality of QWs. The two-interface roughness scattering is also incorporated to make comparison.

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Pucicki, D. "Inhomogeneous GaInNAs quantum wells: their properties and utilization for improving of p-i-n and p-n junction photodetectors." Materials Science-Poland 35, no. 4 (March 20, 2018): 893–902. http://dx.doi.org/10.1515/msp-2017-0110.

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Abstract A theoretical study of electronic structures and optical properties of GaInNAs/GaAs quantum wells has been performed. The inhomogeneous distributions of indium and nitrogen atoms along the growth direction were discussed as the main factors having significant impact on the QWs absorption efficiency. The study was performed by applying the band anticrossing model combined with the envelope function formalism and based on the material parameters which can be found in the literature. Indeed, the electronic band structure of 15 nm thick uniform Ga0.7In0.3N0.02As0.98/GaAs QW was computed together with electronic structures of several types of inhomogeneous QWs, with the same total content of In and N atoms. It was found that presented inhomogeneities lead to significant quantum wells potential modifications and thus to spatial separation of the electrons and holes wave functions. On the other hand, these changes have a significant impact on the absorption coefficient behavior. This influence has been studied on the basis of simulated photoreflectance spectra, which probe the absorption transitions between QW energy subbands. The electronic structure of inhomogeneous QWs under the influence of electric field has also been studied. Two different senses of electric field vector (of p-i-n and n-i-p junctions) have been considered and thus, the improvement of such types of QWs-photodetectors based on inhomogeneous GaInNAs QWs has been proposed.

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Klimov, Victor I., and Moungi G. Bawendi. "Ultrafast Carrier Dynamics, Optical Amplification, and Lasing in Nanocrystal Quantum Dots." MRS Bulletin 26, no. 12 (December 2001): 998–1004. http://dx.doi.org/10.1557/mrs2001.256.

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Semiconductor materials are widely used in both optically and electrically pumped lasers. The use of semiconductor quantum wells (QWs) as optical-gain media has resulted in important advances in laser technology. QWs have a two-dimensional, step-like density of electronic states that is nonzero at the band edge, enabling a higher concentration of carriers to contribute to the band-edge emission and leading to a reduced lasing threshold, improved temperature stability, and a narrower emission line. A further enhancement in the density of the band-edge states and an associated reduction in the lasing threshold are in principle possible using quantum wires and quantum dots (QDs), in which the confinement is in two and three dimensions, respectively. In very small dots, the spacing of the electronic states is much greater than the available thermal energy (strong confinement), inhibiting thermal depopulation of the lowest electronic states. This effect should result in a lasing threshold that is temperatureinsensitive at an excitation level of only 1 electron-hole (e-h) pair per dot on average. Additionally, QDs in the strongconfinement regime have an emission wavelength that is a pronounced function of size, adding the advantage of continuous spectral tunability over a wide energy range simply by changing the size of the dots.

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Kinoshita, A., H. Hirayama, P. Riblet, M. Ainoya, A. Hirata, and Y. Aoyagi. "Emission Enhancement of GaN/AlGaN Single-Quantum-Wells Due to Screening of Piezoelectric Field." MRS Internet Journal of Nitride Semiconductor Research 5, S1 (2000): 682–88. http://dx.doi.org/10.1557/s1092578300004932.

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Photoluminescence (PL) enhancement due to the screening of piezoelectric field induced by Si-doping is systematically studied in GaN/AlGaN quantum wells (QWs) fabricated by metal organic vapor-phase-epitaxy (MOVPE). The PL enhancement ratio of QWs for Si-doped directly into the wells was much larger than that for doped only into the barrier layers. This result shows that the crystal quality of the quantum well is not so damaged by heavy Si-doping, which is different from the cases of GaAs or InP material systems. The PL intensity enhancement ratio was especially large for thick wells. The typical value of the enhancement ratio was 30 times for a 5 nm-thick single QW. The optimum Si-doping concentration was approximately 4×1018 cm−3. From the well width dependence of the PL enhancement ratio and PL peak shift under high excitation conditions, we determined that the dominant effect inducing the PL enhancement is screening of piezoelectric field in the QWs. These results indicate that Si-doping is very effective for the application of GaN/AlGaN QWs to optical devices.

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Quang, Doan Nhat, Nguyen Huyen Tung, Nguyen Trung Hong, and Tran Thi Hai. "Mobility Enhancement in Square Quantum Wells: Symmetric Modulation of the Envelop Wave Function." Communications in Physics 20, no. 3 (August 15, 2010): 193. http://dx.doi.org/10.15625/0868-3166/20/3/2212.

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We present a theoretical study of the effects from symmetric modulation of the envelop wave function on quantum transport in square quantum wells (QWs). Within the variational approach we obtain analytic expressions for the carrier distribution and their scattering in symmetric two-side doped square QWs. Roughness-induced scattering are found significantly weaker than those in the asymmetric one-side doped counterpart. Thus, we propose symmetric modulation of the wave function as an efficient method for enhancement of the roughness-limited QW mobility. Our theory is able to well reproduce the recent experimental data about low-temperature transport of electrons and holes in two-side doped square QWs, e.g., the mobility dependence on the channel width, which have not been explained so far.

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Dubinov, Alexander A., and Vladimir Ya Aleshkin. "Calculation of Modal Gain for Terahertz Lasers Based on HgCdTe Heterostructures with Quantum Wells." International Journal of High Speed Electronics and Systems 25, no. 03n04 (September 2016): 1640018. http://dx.doi.org/10.1142/s0129156416400188.

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In this work we calculate and analyze modal gain for terahertz lasers based on HgCdTe heterostructures with quantum wells (QWs) taking into account the symmetry-enforced light hole-heavy hole mixing at the quantum well interfaces. We have found that modal gain for a structure with 5 HgTe QWs of the 5.2 nm width can be 33 cm−1 at 9 THz.

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Bhattacharya, S., D. De, S. Chowdhury, S. Karmakar, D. K. Basu, S. Pahari, and K. P. Ghatak. "Simple Theoretical Analysis of the Photoemission from Quantum Confined Non-Linear Optical, Optoelectronic, and Related Materials." Journal of Computational and Theoretical Nanoscience 3, no. 2 (April 1, 2006): 280–95. http://dx.doi.org/10.1166/jctn.2006.3010.

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In this paper, an attempt is made to study the photo emission from quantum wells (QWs), quantum well wires (QWWs), and quantum dots (QDs) of non-linear optical materials on the basis of a newly formulated electron dispersion law considering the anisotropies of the effective electron masses, the spin-orbit splitting constants and the presence of the crystal field splitting within the framework of k.p formalism. The results of quantum confined III–V optoelectronic compounds form the special cases of our generalized analysis. The photoemission has also been studied for quantum confined optoelectronic II–VI and stressed materials respectively. It has been found taking quantum confined CdGaAs2, Hg1−xCdxTe, In1−xGaxAsyP1−y lattice matched to InP, CdS, and stressed InSb as examples that the photo emission exhibits plateaus as function of incident photon energy, which is important from experimental point of view, analogous to the same type of plateaus which have been observed in quantum Hall effect in the variation of the quantized Hall resistance with quantizing magnetic field. The photoemission also exhibits quantized variations with changing electron concentration and field thickness, respectively, for all types of quantum confinement. The photoemission is the greatest for QDs and the least for QWs. In addition, the well-known results for bulk specimens of wide-gap materials have also been obtained as special cases from our generalized expressions under certain limiting conditions.

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Kim, Hyun Soo, and Sung Nam Lee. "Homogeneous in Distribution of InGaN/GaN Quantum Wells in High Performance GaN-Based Light-Emitting Devices." Applied Mechanics and Materials 472 (January 2014): 715–19. http://dx.doi.org/10.4028/www.scientific.net/amm.472.715.

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We have investigated the effect of well growth rate on threshold current and slope efficiency of GaN-based laser diodes (LDs). The lasing performance was significantly dependent on optical and crystal quality of In0.08Ga0.92N/ GaN QWs with different well growth rates. The InGaN QWs grown with lower growth rate represented better interface quality and had low surface defects in the InGaN/GaN QW region. In addition, InGaN QWs grown with lower growth rate exhibited the higher optical properties such as the higher PL intensity and the smaller blueshift with increasing excitation power density. The present results suggest that optical and crystal qualities of InGaN/InGaN MQW are significantly improved by lowering well growth rate, resulting in the increase of slope efficiency and the decrease of threshold current density in GaN-based LDs.

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MACHIDA, TAKUYA. "LIMIT THEOREMS FOR A LOCALIZATION MODEL OF 2-STATE QUANTUM WALKS." International Journal of Quantum Information 09, no. 03 (April 2011): 863–74. http://dx.doi.org/10.1142/s0219749911007460.

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We consider 2-state quantum walks (QWs) on the line, which are defined by two matrices. One of the matrices operates the walk at only half-time. In the usual QWs, localization does not occur at all. However, our walk can be localized around the origin. In this paper, we present two limit theorems, that is, one is a stationary distribution and the other is a convergence theorem in distribution.

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Hu, Min, Hailong Wang, and Qian Gong. "The impurity states in different shaped quantum wells under applied electric field." International Journal of Modern Physics B 34, no. 25 (September 15, 2020): 2050224. http://dx.doi.org/10.1142/s0217979220502240.

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In this paper, the impurity states in square, parabolic and V-shaped quantum wells (QWs) are calculated by the plane wave method under the theoretical framework of effective mass envelope function approximation. In different shaped QWs, the impurity binding energies in 1s-like state and 2p-like state have the same trend with the increase of QW width. However, the transition energies of impurity states between 1s-like state and 2p-like state in three shaped QWs are different. When the width of QW is fixed, the transition energy in square QW is the minimum and that in V-shaped QW is the maximum. The effect of electric field is larger for the on-center donor impurity. The effect of electric field on the impurity states is the largest in square QW and the smallest in V-shaped QW.

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Someya, Takao, Katsuyuki Hoshino, Janet C. Harris, Koichi Tachibana, Satoshi Kako, and Yasuhiko Arakawa. "Emission at 247 nm from GaN quantum wells grown by MOCVD." MRS Internet Journal of Nitride Semiconductor Research 5, S1 (2000): 984–89. http://dx.doi.org/10.1557/s1092578300005354.

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Photoluminescence (PL) spectra were measured at room temperature for GaN quantum wells (QWs) with Al0.8Ga0.2N barriers, which were grown by atmospheric-pressure metal organic chemical vapor deposition (MOCVD). The thickness of the GaN QW layers was systematically varied from one monolayer to four monolayers. We clearly observed a PL peak at a wavelength as short as 247 nm (5.03 eV) from one monolayer-thick QWs. The effective confinement energy is as large as 1.63 eV.

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CHRISTIANEN, PETER C. M. "SEMICONDUCTOR NANOSTRUCTURES IN HIGH MAGNETIC FIELDS: RECENT RESULTS AT HFML NIJMEGEN." International Journal of Modern Physics B 23, no. 12n13 (May 20, 2009): 2573–74. http://dx.doi.org/10.1142/s0217979209062001.

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A short overview of the current experimental facilities at the HFML Nijmegen, including an update on the planned development of a 45 T Hybrid magnet in conjunction with a Free Electron Laser, was presented. That was followed by a brief highlight of recent results on the high field physical properties of semiconductor nanostructures, such as quantum rings1 and dots,2 graphene3,4 and organic nanostructures.5 The majority of the talk was devoted to the investigation of negatively charged excitons (negative trions, two electrons bound to one hole) in semiconductor quantum wells in high magnetic fields. A comprehensive overview of photoluminescence (PL) experiments on GaAs and CdTe quantum wells (QWs) of variable well widths, containing a low density electron gas (2DEG) was presented. Particular interest was given to the magnetic field range where the ground state of negative trions is changing from a singlet (both electrons having opposite spin) to a triplet (parallel electron spins) state. Using polarized magneto-PL (excitation) and reflectivity spectroscopy we have identified (for both GaAs and CdTe QWs) the four typical excitonic peaks, usually denoted as the singlet, dark triplet and bright triplet trion peaks, as well as the neutral exciton peak. All peaks exhibit a pronounced dependence on polarization, 2DEG density and temperature. CdTe QWs exhibit all four peaks at the entire field range used (< 44 T), whereas the dark triplet emission disappears at high fields for GaAs QWs. We have determined the field strength at which the singlet-triplet crossover occurs for all QWs, which allows us to critically compare our experimental results with theoretical predictions. Remarkably, the actual singlet-triplet transition is hidden in GaAs QWs and a narrow (12 nm) CdTe QW. Since the PL emission energy equals the energy difference between the initial (trion) and final (electron) states, the PL lines themselves do not cross at the singlet-triplet crossover as a result of the different Zeeman energies of the final electron states.6 In contrast the cross-over is directly visible in the PL lines of a wide (20 nm) CdTe QW. This behaviour can be readily understood by the dependence of the electron- and hole g -factors on well width and host material. Note from Publisher: This article contains the abstract only.

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Sizov, F. F., V. V. Tetyorkin, J. V. Gumenjuk-Sichevskaya, and M. V. Apatskaya. "Properties of PbTe/PbSnTe multiple QWs." Superlattices and Microstructures 9, no. 4 (January 1991): 483–86. http://dx.doi.org/10.1016/0749-6036(91)90175-q.

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Ozturk, Emine. "Comparison of Ga1−xAlxAs/GaAs and Ga1−xlnxAs/GaAs quantum wells as dependent on Al and In concentrations under intense laser field." International Journal of Modern Physics B 29, no. 27 (October 27, 2015): 1550187. http://dx.doi.org/10.1142/s0217979215501878.

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In this study, the electronic properties of [Formula: see text] and [Formula: see text] quantum wells (QWs) are theoretically calculated as dependent on the intense laser field (ILF) and x-concentration value within the effective mass approximation and the envelope function approach. Our results show that the shape of confined potential profile, the energy differences and the dipole moment matrix elements are changed as dependent on the ILF and x-value. The energy levels of different QWs give different values by increasing ILF amplitudes and x-concentrations. In the case of QW under ILF, there are significant modifications of the electrical states of QWs, due to the effects of confining the potential resulting from the applied ILF. I say that the variation of [Formula: see text] QW under ILF is more than [Formula: see text] QW. The numerical results show that the structure parameters have a great effect on the electronic characteristics of these QW structures.

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Kiumi, Chusei. "A new type of quantum walks based on decomposing quantum states." quantum Information and Computation 21, no. 7&8 (June 2021): 541–56. http://dx.doi.org/10.26421/qic21.7-8-1.

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In this paper, the 2-state decomposed-type quantum walk (DQW) on a line is introduced as an extension of the 2-state quantum walk (QW). The time evolution of the DQW is defined with two different matrices, one is assigned to a real component, and the other is assigned to an imaginary component of the quantum state. Unlike the ordinary 2-state QWs, localization and the spreading phenomenon can coincide in DQWs. Additionally, a DQW can always be converted to the corresponding 4-state QW with identical probability measures. In other words, a class of 4-state QWs can be realized by DQWs with 2 states. In this work, we reveal that there is a 2-state DQW corresponding to the 4-state Grover walk. Then, we derive the weak limit theorem of the class of DQWs corresponding to 4-state QWs which can be regarded as the generalized Grover walks.

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Md Sahar, Mohd Ann Amirul Zulffiqal, Zainuriah Hassan, Sha Shiong Ng, Way Foong Lim, Khai Shenn Lau, Ezzah Azimah Alias, Mohd Anas Ahmad, Nur Atiqah Hamzah, and Rahil Izzati Mohd Asri. "Effects of V/III ratio of InGaN quantum well at high growth temperature for near ultraviolet light emitting diodes." Microelectronics International 38, no. 3 (July 19, 2021): 119–26. http://dx.doi.org/10.1108/mi-02-2021-0017.

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Purpose The aims of this paper is to study the effects of the V/III ratio of indium gallium nitride (InGaN) quantum wells (QWs) on the structural, optical and electrical properties of near-ultraviolet light-emitting diode (NUV-LED). Design/methodology/approach InGaN-based NUV-LED is successfully grown on the c-plane patterned sapphire substrate at atmospheric pressure using metal organic chemical vapor deposition. Findings The indium composition and thickness of InGaN QWs increased as the V/III ratio increased from 20871 to 11824, according to high-resolution X-ray diffraction. The V/III ratio was also found to have an important effect on the surface morphology of the InGaN QWs and thus the surface morphology of the subsequent layers. Apart from that, the electroluminescence measurement revealed that the V/III ratio had a major impact on the light output power (LOP) and the emission peak wavelength of the NUV-LED. The LOP increased by up to 53% at 100 mA, and the emission peak wavelength of the NUV-LED changed to a longer wavelength as the V/III ratio decreased from 20871 to 11824. Originality/value This study discovered a relation between the V/III ratio and the properties of QWs, which resulted in the LOP enhancement of the NUV-LED. High TMIn flow rates, which produced a low V/III ratio, contribute to the increased LOP of NUV-LED.

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Chaqmaqchee, Faten A. "Long-wavelength GaInNAs/GaAs Vertical-cavity Surface-emitting Laser for Communication Applications." ARO-THE SCIENTIFIC JOURNAL OF KOYA UNIVERSITY 8, no. 1 (June 30, 2020): 107–11. http://dx.doi.org/10.14500/aro.10627.

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This paper presents a comprehensive study of optical and electrical properties of vertical-cavity surface-emitting lasers(VCSELS) for long wavelength communication applications. The device consists of GaInNAs/GaAs multi-quantum wells QWs that enclosed between standard top and bottom epitaxially grown on AlGaAs/GaAs distributed Bragg reflectors. The impact of driven currents and injecting optical powers through QWs layers on the output light emission is addressed. Room temperature spectra measurements are performed at various applied currents using 980 nm pump laser and maximum intensity amplitude at around 21 dB was achieved.

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SHALYGIN, V. A., L. E. VOROBJEV, V. Yu. PANEVIN, D. A. FIRSOV, S. HANNA, H. KNIELING, A. SEILMEIER, et al. "EXCITED STATE PHOTOLUMINESCENCE IN STEPPED InGaAs/AlGaAs QUANTUM WELLS UNDER PICOSECOND EXCITATION." International Journal of Nanoscience 02, no. 06 (December 2003): 427–35. http://dx.doi.org/10.1142/s0219581x03001528.

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The technique of photoluminescence (PL) studies based on intense picosecond excitation of electron–hole pairs is applied to investigate the electron energy structure including the positions of high-lying excited levels in stepped quantum wells (QWs). The spectra of PL in regimes of spontaneous and stimulated emission are studied under different excitation levels and light polarizations. Of special interest are intense photoluminescence signals from excited subbands. The feasibility of a e3–e2 intersubband population inversion in stepped QWs is demonstrated and the influence of Auger recombination was examined.

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Feng, Yulong, Zhizhong Chen, Chengcheng Li, Yifan Chen, Jinglin Zhan, Yiyong Chen, Jingxin Nie, et al. "Effect of dipole polarization orientation on surface plasmon coupling with green emitting quantum wells by cathodoluminescence." RSC Advances 8, no. 29 (2018): 16370–77. http://dx.doi.org/10.1039/c8ra01859f.

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LARRAMENDI, ERICK M., EDGAR LÓPEZ-LUNA, OSVALDO DE MELO, and ISAAC HERNÁNDEZ-CALDERÓN. "INTERACTION BETWEEN Zn AND Cd ATOMS DURING THE ATOMIC LAYER EPITAXY GROWTH OF CdZnTe/ZnTe QUANTUM WELLS." Surface Review and Letters 09, no. 05n06 (October 2002): 1725–28. http://dx.doi.org/10.1142/s0218625x02004293.

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Layers of 6 and 16 Cd–Te–Zn–Te periods were grown by atomic layer epitaxy (ALE) within ZnTe thin films. Different samples were grown at substrate temperatures of 260 and 290°C. Information about the kinetics of growth and surface reconstruction during the ALE growth of CdTe and ZnTe films, and Cd–Te–Zn–Te periods was obtained by means of reflection high-energy electron diffraction (RHEED) experiments and through the analysis of the temporal behavior of the intensities of several features of the RHEED patterns. The photoluminescence of the sample grown at 260°C presents two narrow and intense peaks corresponding to emission from quantum wells (QWs). However, the spectrum of the samples grown at 290°C does not show any feature associated with QWs, the spectrum resembling that of a ZnTe film. Cd replacement by Zn atoms explains the absence of the CdZnTe QWs at 290°C and a lower Cd content than expected at 260°C. The replacement of Cd atoms by Zn atoms in the CdTe surface was clearly demonstrated by Auger experiments.

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Podili, Prashanth, K. K. Pattanaik, and Prashanth Singh Rana. "BAT and Hybrid BAT Meta-Heuristic for Quality of Service-Based Web Service Selection." Journal of Intelligent Systems 26, no. 1 (January 1, 2017): 123–37. http://dx.doi.org/10.1515/jisys-2015-0032.

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AbstractEfficient QoS-based service selection from a pool of functionally substitutable web services (WS) for constructing composite WS is important for an efficient business process. Service composition based on diverse QoS requirements is a multi-objective optimization problem. Meta-heuristic techniques such as genetic algorithm (GA), particle swarm optimization (PSO), and variants of PSO have been extensively used for solving multi-objective optimization problems. The efficiency of any such meta-heuristic techniques lies with their rate of convergence and execution time. This article evaluates the efficiency of BAT and Hybrid BAT algorithms against the existing GA and Discrete PSO techniques in the context of service selection problems. The proposed algorithms are tested on the QWS data set to select the best fit services in terms of maximum aggregated end-to-end QoS parameters. Hybrid BAT is found to be efficient for service composition.

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Kuo, Ting Wei, Ling Min Kong, Zhe Chuan Feng, Wei Liu, Soo Jin Chua, and Ying Sheng Huang. "Photoluminescence Properties of InGaN/GaN Multiple Quantum Well Light Emitting Diodes by Metalorganic Chemical Vapor Deposition." Advanced Materials Research 306-307 (August 2011): 1133–37. http://dx.doi.org/10.4028/www.scientific.net/amr.306-307.1133.

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Luminescence properties of blue emission InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs), grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD), were studied by time-resolved photoluminescence (TRPL) spectroscopic technique. Samples involved have similar basic structures of three QWs but different well-composition and barrier/well dimensions. TRPL results show that PL intensity and decay time increase with the number of QWs and the indium composition. Correlation of physical properties with crystalline perfection open the way for optimized designs of InGaN MQW LED, with controlled the indium composition and QW numbers.

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Cibert, J., P. Kossacki, A. Haury, D. Ferrand, A. Wasiela, Y. Merle d'Aubigné, A. Arnoult, S. Tatarenko, and T. Dietl. "Ferromagnetic transition in II–VI semimagnetic QWs." Journal of Crystal Growth 201-202 (May 1999): 670–73. http://dx.doi.org/10.1016/s0022-0248(98)01444-4.

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Yakovlev, D. R., J. Puls, G. V. Mikhailov, G. V. Astakhov, V. P. Kochereshko, W. Ossau, J. Nürnberger, W. Faschinger, F. Henneberger, and G. Landwehr. "Charged Exciton Dynamics in ZnSe/ZnMgSSe QWs." physica status solidi (a) 178, no. 1 (March 2000): 501–5. http://dx.doi.org/10.1002/1521-396x(200003)178:1<501::aid-pssa501>3.0.co;2-d.

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Konno, Norio, and Masato Takei. "The non-uniform stationary measure for discrete-time quantum walks in one dimension." Quantum Information and Computation 15, no. 11&12 (September 2015): 1060–75. http://dx.doi.org/10.26421/qic15.11-12-12.

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We consider stationary measures of the one-dimensional discrete-time quantum walks (QWs) with two chiralities, which is defined by a 2 $\times$ 2 unitary matrix $U$. In our previous paper \cite{Konno2014}, we proved that any uniform measure becomes the stationary measure of the QW by solving the corresponding eigenvalue problem. This paper reports that non-uniform measures are also stationary measures of the QW except when $U$ is diagonal. For diagonal matrices, we show that any stationary measure is uniform. Moreover, we prove that any uniform measure becomes a stationary measure for more general QWs not by solving the eigenvalue problem but by a simple argument.

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Gallacher, K., L. Baldassarre, A. Samarelli, R. W. Millar, A. Ballabio, J. Frigerio, G. Isella, et al. "Ge-on-Si Photonics for Mid-infrared Sensing Applications." MRS Advances 1, no. 48 (2016): 3269–79. http://dx.doi.org/10.1557/adv.2016.391.

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ABSTRACTThere is significant interest to develop cheap CMOS compatible sensors that operate in the mid-infrared (MIR). To meet these requirements, Ge-on-Si is proving to be an exciting platform. There is the potential to realize waveguide integrated quantum well infrared photodetectors (QWIPs) based on Ge quantum wells (QWs). Intersubband absorption from p-Ge QWs has been demonstrated in the important atmospheric transmission window of 8-13 μm. An alternative strategy for sensing in the MIR is demonstrated through highly n-type doped Ge plasmonic antennas. These antennas demonstrate vibrational sensing of polydimethylsiloxane (PDMS) spin coated layers at 12.5 μm wavelength. These demonstrate enhanced sensing capabilities due to the localized hot spots of the antenna resonant modes.

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Liang, Rui, Leon Shterengas, Gela Kipshidze, Takashi Hosoda, Sergey Suchalkin, and Gregory Belenky. "Novel Cascade Diode Lasers Based on Type-I Quantum Wells." International Journal of High Speed Electronics and Systems 23, no. 03n04 (September 2014): 1450022. http://dx.doi.org/10.1142/s0129156414500220.

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A novel approach for cascade diode lasers was developed based on type-I quantum wells (QWs). This design adopted the leaky window effect in the GaSb / InAs band alignment for cascade pumping, and exploits the carriers recycling by the cascade pumping and the high optical gain of the type-I QWs. Two-stage cascade lasers were designed and fabricated for 2.45 and 3.0 μm, demonstrating twofold improvement in the internal efficiency. Record continuous-wave (CW) output power of 1.2 W for 2.45 um and 590 mW for 3.0 um were achieved in room temperature (RT), and the devices operate with higher power conversion efficiency at high power level, compared to conventional single-stage diode lasers.

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Zheng, Changda, Li Wang, Chunlan Mo, Wenqing Fang, and Fengyi Jiang. "Effect of Same-Temperature GaN Cap Layer on the InGaN/GaN Multiquantum Well of Green Light-Emitting Diode on Silicon Substrate." Scientific World Journal 2013 (2013): 1–4. http://dx.doi.org/10.1155/2013/538297.

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GaN green LED was grown on Si (111) substrate by MOCVD. To enhance the quality of InGaN/GaN MQWs, same-temperature (ST) GaN protection layers with different thickness of 8 Å, 15 Å, and 30 Å were induced after the InGaN quantum wells (QWs) layer. Results show that a relative thicker cap layer is benefit to get InGaN QWs with higher In percent at fixed well temperature and obtain better QW/QB interface. As the cap thickness increases, the indium distribution becomes homogeneous as verified by fluorescence microscope (FLM). The interface of MQWs turns to be abrupt from XRD analysis. The intensity of photoluminescence (PL) spectrum is increased and the FWHM becomes narrow.

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Yu, Hongyan, Jiaoqing Pan, Xuliang Zhou, Hui Wang, Liang Xie, and Wei Wang. "A Widely Tunable Three-Section DBR Lasers for Multi-Species Gas Detection." Applied Sciences 11, no. 6 (March 15, 2021): 2618. http://dx.doi.org/10.3390/app11062618.

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We demonstrate a widely tunable distributed Bragg reflector (DBR) laser operating at 1.8-µm, in which the DBR section was butt-jointed InGaAsP (λ = 1.45 μm) material. Through current and temperature tuning, a widely tuning range of over 11 nm with a side mode suppression ratio (SMSR) higher than 30 dB is obtained. Utilizing this DBR laser, the water and methane detection experiment has been successfully implemented, which illustrates the potential capacity of such DBR laser as the light source used for multispecies gas sensing. The work also illustrates that the butt-joint active-passive integration technology developed for the InGaAsP quantum-wells (QWs) can be successfully applied in the InGaAs QWs.

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Hirayama, H., and Y. Aoyagi. "Optical Properties of Si-DOPED AlxGa1−xN/AlyGa1−yN (x=0.24−0.53, y=0.11) Multi-Quantum-Well Structures." MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 405–10. http://dx.doi.org/10.1557/s1092578300002805.

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We demonstrate strong ultraviolet (UV) (280-330nm) photoluminescence (PL) emission from multi-quantum-well (MQW) structures consisting of AlGaN active layers fabricated by metal-organic chemical-vapor-deposition (MOCVD). Si-doping is shown to be very effective in order to enhance the PL emission of AlGaN QWs. We found that the optimum values of well thickness and Si-doping concentration of AlxGa1−xN/AlyGa1−yN (x=0.24−0.53, y=0.11) MQW structure for efficient emission were approximately 3nm and 2×1019cm−3, respectively. In addition, the PL intensities of AlGaN, GaN and InGaN quantum well structures are compared. We have found that the PL emission at 77K from a Al0.53Ga0.47N/Al0.11Ga0.89N MQW is as strong as that of InGaN QWs.

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KIM, H. J., and K. S. YI. "MAGNETIZATION OF DIGITALLY Mn-DOPED DILUTED MAGNETIC SEMICONDUCTOR QUANTUM WELLS." International Journal of Modern Physics B 18, no. 27n29 (November 30, 2004): 3757–60. http://dx.doi.org/10.1142/s0217979204027414.

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We present spin-resolved electronic properties of digitally Mn -doped diluted magnetic semiconductor (DMS) quantum wells (QWs) with an emphasis on the control of spontaneous magnetization and spin carrier distributions in terms of QW structure parameters and doping profiles of the magnetic ions. A combined Schrödinger and Poisson equation is solved numerically to obtain self-consistent subband wavefunctions and energies of the holes in the DMS QWs. Self-consistent spin-resolved subband structure shows that (i) the spatial distributions of the majority and minority spin carriers are separated in the DMS QW below the Curie temperature and (ii) the spontaneous magnetization of the Mn -doped magnetic nanostructure depends sensitively on doping profiles of the magnetic ion and the strength of exchange couplings.

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Wu, Zhengyuan, Tienmo Shih, Jinchai Li, Pengfei Tian, Ran Liu, Junyong Kang, and Zhilai Fang. "Improved semipolar green InGaN/GaN quantum wells on asymmetrically grown (112̄2) GaN templates and their correlations." CrystEngComm 20, no. 14 (2018): 2053–59. http://dx.doi.org/10.1039/c8ce00151k.

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Asymmetric island sidewall growth (AISG) is employed to reduce the threading defect density and to modify the surface/interface properties of semipolar GaN templates and InGaN/GaN quantum wells (QWs).

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Journal articles on the topic 'QWs'

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