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AlGaAs/GaAs solar cell with CNT transport layer: numerical simulation
摘要： AlGaAs/GaAs solar cells (SC) was modeled. Conventional SC was compared with structure with the thinner emitter. SC with additional CNT transport layer was simulated and compared with SC without it. The simulation was carried out with different geometry of the contacts and light flux. CNT transport layer has allowed achieving an increase in SCs efficiency up to 1.7% compared with metal contact grid.
关键词： CNT transport layer,numerical simulation,AlGaAs/GaAs solar cell
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All-Optical Ultrafast Control of Second Harmonic Generation in AlGaAs Nanopillars
摘要： All-dielectric nanophotonics has recently raised an increasing interest because the optical response of high-permittivity dielectric nanoparticles exhibits negligible dissipative losses and strong magnetic multipole resonances [1-4] in the visible and near-IR. We recently reported a second harmonic generation (SHG) conversion efficiency higher than 10-5 at (cid:79)= 1554 nm (pump intensity (cid:124) 1.6 GW/cm2; pulse width (cid:124) 150 fs; repetition rate = 80 MHz) in all-dielectric Al0.18Ga0.82As-on-AlOx nanodisks [5-7]. Such a remarkable efficiency is achieved thanks to the exploitation of magnetic and electric resonances emerging at coincidence with both the pump and SHG wavelength. In addition, the choice of both the pump and, consequently, the SHG ((cid:124) 777 nm) wavelength, set below the energy of the material bandgap, allow minimizing the two-photon absorption of the pump and the re-absorption of the SHG. Here, we demonstrate the potential for the all-optical modulation of the SHG. First, we study the behavior of the emitted SHG signal when the nanoantennas are concurrently illuminated with a low-power (< 300 (cid:80)W) continuous wave (CW) laser with energy above the bandgap ((cid:124) 3.2 eV, 405 nm wavelength). We observe variations in the SHG yield of the nanoantennas up to 60%. Figure 1a shows the SHG differential map acquired on an array of nanopillars with variable radius (r). Figure 1b shows the overall SHG intensity (dashed line) as well as the SHG modulation (solid blue line) as a function of r. While SHG from the smaller nanopillar (r = 205 nm) is decreased by about 60% under a 300 (cid:80)W CW pump beam, the 220-nm-radius nanopillar show a 30% SHG enhancement. We also investigated the ultrafast modulation of the SHG in a pump-probe experiment, where the pump is an ultrashort pulse at (cid:79)= 510 nm (above material bandgap), while the probe is a time-delayed pulse at (cid:79)= 1550 nm generating the SHG, to study the SHG dynamics when the pillars are brought out of equilibrium and a transient plasma is photoinjected in the dielectric. Time-traces of the SHG as a function of the pump-probe delay are shown in Figure 1c. We measured an ultrafast SHG quenching (< 0.5 ps) and slower (10 to 100 ps) recovery times, which strongly depend on the nanopillars, hence on the resonances involved. Our results allow gaining further insight into the photophysics of the nonlinear emission in these nanoscale systems and pave the way to the all-optical control of nanoscale nonlinear photonic devices for data storage with AlGaAs-on-insulator all-dielectric platforms.
关键词： Second harmonic generation,All-optical modulation,Nanopillars,All-dielectric nanophotonics,AlGaAs,SHG
更新于2025-09-12 10:27:22
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Improved spectral and temporal response of MSM photodetectors fabricated on MOCVD grown spontaneous AlGaAs superlattice
摘要： A co-planar metal-semiconductor-metal nonsymmetrical back to back Schottky diode photodetector using natural superlattice AlGaAs grown by metalorganic vapor phase epitaxy on GaAs (100) has been reported. The detection efficiency and photoresponse of the superlattice based device are found significantly superior compared to the one based on high temperature annealed homogeneous AlGaAs. Under a forward bias of 1 V, the peak values of responsivity, detectivity and sensitivity were 10.133 mA/W, 7.6 × 1011 cmHz1/2W?1, 81.06 cm2/W for the device with as-grown natural superlattice and 1.14 mA/W, 7.05 × 1010 cmHz1/2W?1, 2.82 cm2/W for the device with homogeneous composition of AlGaAs, respectively. Besides, the device with natural superlattice structure showed much faster response to the pulsed light with rise and decay time of 560 μs and 1 ms as compared to 2 and 7 ms, respectively for the device with disordered bulk AlGaAs. The superior spectral and temporal characteristics of the device are explained by a model based on a third diode representing the net effect due to the superlattice modulations along with two Schottky diodes at the metal-semiconductor junctions. The third barrier, which is basically due to the periodic modulation in aluminium composition, plays an important role in enhancement of the photocurrent owing to the activation of the superlattice channels under light while keeping the dark current small. The fast sweeping of the photogenerated carries by the intrinsic electric field at the heterointerfaces in the active semiconducting layer makes the characteristic times of the device with the superlattice structures much smaller than one with homogeneous AlGaAs. Degradation in photoresponse and speed is attributed to the interdiffusion as an effect of thermal annealing.
关键词： AlGaAs/GaAs,Spectral response,Metal-semiconductor-metal photodetector,Natural superlattice,Temporal response
更新于2025-09-12 10:27:22
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[IEEE 2019 1st International Conference on Advances in Science, Engineering and Robotics Technology (ICASERT) - Dhaka, Bangladesh (2019.5.3-2019.5.5)] 2019 1st International Conference on Advances in Science, Engineering and Robotics Technology (ICASERT) - Design and Optimization of AlGaAs/InP Multi-junction Solar Cell
摘要： A structure for AlxGa1-xAs/InP multi-junction solar cell is proposed by using numerical simulation and the simulation is done with the help of Analysis of Microelectronic and Photonic Structures (AMPS-1D) simulator. The thickness of p-layer of AlxGa1-xAs top cell is varied from 20 nm to 150 nm keeping the n-layer thickness at a constant value of 800 nm. The thickness of n-layer of InP bottom cell is varied from 100 nm to 7000 nm and p-layer thickness is fixed at 200 nm. The band gap of AlxGa1-xAs top cell absorber layer is varied from 1.42 eV to 1.79 eV. The highest power conversion efficiency (PCE) obtained is 35.643% (Voc=2.385 V, Jsc = 15.789 mA/cm2, FF = 0.88). The operating temperature is also varied from 0 °C to 70 °C. We observed that with the increase in operating temperature, the normalized open circuit voltage decreased almost linearly which shows better stability of this proposed multi-junction solar cell.
关键词： AlGaAs/InP,AMPS-1D simulation,thermal stability,power conversion efficiency (PCE),fill factor (FF)
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Strong Enhancement of Light Extraction Efficiency in Sub-Wavelength AlGaAs/GaAs Vertical-Emitting Nanopillars
摘要： Scaling down active nanophotonic devices, namely nano-lasers and nano-light-emitting diodes (nanoLEDs), to deep sub-micrometer sizes, is crucial to achieve small footprint (<1 μm2), low energy consumption (<10 fJ/bit), and efficient (>10%) light sources, as needed for future compact photonic integrated circuits for optical communications [1], and biosensing and bioimaging applications [2]. As the surface-to-volume ratio of these nanoscale sources increases substantially, among the numerous challenges, strong non-radiative processes and difficulties in extracting the light have been shown to have a detrimental effect on the external quantum efficiencies of nanoLEDs and nanolasers [3]. Although there has been intense research, particularly in light-enhancement and out-coupling methods, using for example 2D photonic crystals [4], optical nanoantennas [5], or nanowaveguides integrated with grating couplers [3], these approaches are extremely challenging to implement when the size of the light-emitting structures is drastically reduced to the deep-subwavelength (<<λ/3) scale. In this work, we report a strong enhanced signal at λ~670 nm in vertical-emitting undoped AlGaAs/GaAs/AlGaAs tapered pillars in a GaAs substrate, Fig. 1(a), when the emitting nominal area is decreased to the sub-μm scale. Vertical-emitting pillars ranging from 200 nm to 8 μm lateral width were fabricated using e-beam lithography and dry etching techniques and characterized using a micro-photoluminescence (PL) microscope with λ=561 nm laser excitation. Figure 1(b) shows examples of emission images for both optically pumped micropillars (top) and nanopillars (bottom) (the respective intensity profiles are shown inset). For the case of micropillars, clearly the light emission is reduced as the diameter decreases following a typical scaling law, d 2, of planar LEDs. However, as d is reduced from 4 μm to 0.2 μm sizes, particularly in the range of 300 nm < d < 400 nm, although the nominal emission area is reduced by a factor of more than 100, the intensity is reduced only by ~10 times. For example, the emitting intensity peaks for pillars with d=360 nm, and the integrated intensity is comparable to pillars with d~1 μm sizes. This strongly deviates from the d 2 dependence observed for micropillars, resulting in a 27-fold enhancement of emission. This striking effect is summarized in Fig. 1(c). Our FDTD simulations for a tapered d=360 nm nanopillar, Fig. 1(a)(bottom), indicate this enhancement is a result of a 3-fold effect: i) suppression of optical modes due to lateral size reduction, ii) efficient out-coupling to air, and iii) more directed emission of tapered pillars. Notably, as shown in the blue circles of Fig. 1(c), the emission can be further improved after surface passivation with (NH4)2S and dielectric capping with a ~50 nm SiO2 layer. For the case of sub-μm pillars, a 3-fold improvement of light emission is achieved as compared with unpassivated samples. In summary, a large improvement of light-extraction in sub-λ vertical-emitting nanopillars is achieved. This pronounced effect enables bright emission in nanoscale devices comparable to the performance of μm-sized devices. This result, combined with the suppression of surface recombination, is crucial for the future development of high-performance nanoscale optoelectronic devices for low-power optical interconnects, supporting the realization of room-temperature highly efficient light sources in photonic integrated circuits.
关键词： sub-wavelength,nanophotonics,vertical-emitting nanopillars,AlGaAs/GaAs,light extraction efficiency
更新于2025-09-11 14:15:04
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Terahertz emission from a weakly-coupled GaAs/AlGaAs superlattice biased into three different modes of current self-oscillations
摘要： Radio-frequency modulated terahertz (THz) emission power from weakly-coupled GaAs/AlGaAs superlattice (SL) has been increased by parallel connection of several SL mesas. Each SL mesa is a self-oscillator with its own oscillation frequency and mode. In coupled non-identical SL mesas biased at different voltages within the hysteresis loop the chaotic, quasiperiodic and frequency-locked modes of self-oscillations of current arise. THz emission was detected when three connected in parallel SL mesas were biased into the frequency-locked and quasiperiodic modes of self-oscillations of current, while in the chaotic mode of those it falls to the noise level.
关键词： current self-oscillations,quasiperiodic mode,terahertz emission,frequency-locked mode,GaAs/AlGaAs superlattice,chaotic mode
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Integrated Semiconductor Quantum Photonics
摘要： For fundamental tests of quantum physics as well as for quantum communications, non-classical states of light are an important tool. In this talk, we will present our work on developing nonlinear AlGaAs waveguides into a platform for quantum photonics in semiconductors. Most III-V semiconductors exhibit a large second-order optical nonlinearity, but phase-matching the nonlinear interaction is notoriously difficult. As a solution Bragg-reflection waveguides allow efficient creation of photon pairs through spontaneous parametric down-conversion. They have the potential to be homogeneously integrated with a pump laser and passive and active components on the chip. In our waveguides, we can create high-fidelity polarization [1] and time-bin entangled [2] photon pairs, which cover a large frequency band in the low-loss telecommunication window, suitable for serving multiple users through wavelength division multiplexing. For all our applications, it is important that we can design the desired linear and nonlinear properties, which in turn makes precise characterization necessary. For this purpose, we have developed a Fourier-transform Fabry-Perot spectroscopy technique [3], which yields the relevant device parameters with superior accuracy. We will further present our results on devices that integrate electrically injected lasers and the nonlinear conversion. A layer of quaternary quantum dots acts as the gain medium in a Fabry-Perot waveguide laser, which lases at room temperature in the Bragg mode, i.e. the pump mode for creating photon pairs. We will close with an outlook on further device integration towards a complete semiconductor quantum photonics platform.
关键词： AlGaAs waveguides,photon pairs,Bragg-reflection waveguides,quantum photonics,Fourier-transform Fabry-Perot spectroscopy,spontaneous parametric down-conversion
更新于2025-09-11 14:15:04
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Quantum Dots - Theory and Applications || Quantum Dots Prepared by Droplet Epitaxial Method
摘要： In this work, we are dealing with the droplet epitaxially prepared quantum dots. This technology is not only an alternative way of the strain induced technique to prepare quantum dots, but it allows us to make various shaped nano structures from various material. The present paper deals not only with the so called conventional shaped quantum dot but also with the ring shaped dot, with the inverted dot and with dot molecules as well. Their thechnology, opto-electronical and the structural properties are also discussed.
关键词： MBE,QD,AlGaAs,droplet epitaxy,AlAs,GaAs
更新于2025-09-11 14:15:04
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[IEEE 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Sao Paulo, Brazil (2019.10.7-2019.10.9)] 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Fabrication of cylindrical resonant microcavities using the confinement provided by partially oxidized AlGaAs/GaAs layers
摘要： Two different interfaces for optical con?nement in GaAs resonators (air/GaAs/air, air/GaAs/AlOx) are compared in cylindrical microstructures with 10 μm of diameter. The AlOx is obtained by the lateral oxidation of Al0.9Ga0.1As layers. The spectrum of the resonators is obtained using a tapered ?ber system in the wavelength range between 1470 nm and 1610 nm. The modal separation agrees with simulations. The quality factor for the cylindrical microstructures having air/GaAs/air interface is almost twice the value for the case of AlOx interface. Since it is expected that surface recombination velocity is reduced by a factor of ten for this last case, these structures are expected to be suitable for the development of active resonators.
关键词： whispering gallery modes,quality factor,microdisk,oxidation of AlGaAs
更新于2025-09-11 14:15:04
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Temporal stability and absolute composition issues in molecular beam epitaxy of AlGaAs/GaAs THz QCL
摘要： The operation of the terahertz quantum cascade lasers (THz QCL) is strongly dependent on the repeatable fabrication of the well and barrier layers with the certain thicknesses throughout the whole active region stack epitaxial growth. This emphasizes the importance of the strict control of the growth rates and the stability of Si and group III effusion cell fluxes during growth [1]. It was reported [2] that two THz QCLs based on nominally identical multilayer heterostructures Al0.15Ga0.85As/GaAs emit at the different frequencies of 2.59 and 2.75 THz because of unintentional small deviations in the GaAs and AlAs growth rates (4 and 1.6 % respectively). Authors [3] determined the thickness tolerance for working lasing heterostructures to be minimally above 2% while the structures with thickness deviation 4.3 and 6.5 % are not lasing. In [4] the Ga cell temperature has to be increased to maintain a GaAs constant growth rate while the Al cell temperature remains nearly constant because variation in AlAs growth rate can be neglected. By using such growth rate compensation technique the two nominally identical structures approximately 10 mkm overall thick were found to show thickness difference of ~ 1 %. Thus calibration procedures and accurate analysis techniques become crucial to provide enhanced metrology possibilities.
关键词： molecular beam epitaxy,metrology,AlGaAs/GaAs,terahertz quantum cascade lasers,growth rates
更新于2025-09-10 09:29:36