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Investigation into the current loss in InAs/GaAs quantum dot solar cells with Si-doped quantum dots
摘要： Our previous studies have shown that introducing Si doping in quantum dots (QDs) can help QD solar cells achieve higher voltage. However, this improvement came at the cost of current loss. In this work, we continue to investigate the cause of the current loss and propose a method to recover it without compromising the voltage. Photoluminescence measurements have confirmed that optimizing the thickness of the GaAs layers in the i-region can lead to strong current gain (~14%) with minimal voltage loss (<3%) and alteration of the QD quality. The capacitance–voltage measurement results support that the current gain mainly originates from the increased depletion width.
关键词： MBE,current recovery,QDSC
更新于2025-09-19 17:13:59
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In-Situ Tailoring of Vertically Coupled InAs p-i-p Quantum-Dot Infrared Photodetectors: Toward Homogeneous Dot Size Distribution and Minimization of Ina??Ga Intermixing
摘要： The authors report a detailed analysis of an epitaxial growth technique for Indium Arsenide (InAs) Quantum-dot infrared photodetectors to circumvent the detrimental effects arising from the progressively increasing dot-size in vertically coupled heterostructures. Constant overgrowth percentage of the vertically coupled dot-layers has been achieved with the implementation of the growth strategy, which has been validated by cross-sectional transmission electron microscopy (X-TEM) images of the samples. The optical characteristics of these samples have been analyzed through photoluminescence spectroscopy and photoluminescence excitation spectroscopy (PL and PLE) measurements which show longer wavelength response and reduced full width at half-maxima (FWHM) upon implementation of the growth strategy. X-TEM, in-plane and out-of-plane high resolution X-ray diffraction (HR-XRD) measurements suggest morphological improvement upon implementation of the growth strategy, with a reduction in the Indium desorption and lowering of defects and dislocation densities. Excellent correlation has been found between the different experimental results and also their theoretical simulations. The fabricated single-pixel photodetectors at low temperature (T=14K) show a broad response extending up to the MWIR region (~4.5μm) for one of the samples. Also, a strong spectral response in the SWIR region is obtained even at room temperature (T=300K). The highest responsivity (Rp) and specific detectivity (D*) values obtained are 166.17 A/W and 8.39 x 1010 cmHz1/2W-1 at a bias of 5V and 300K temperature.
关键词： p-i-p infrared photodetectors,InAs Quantum Dots,MBE growth strategy,homogenous dot size distribution,room temperature spectral response,In-Ga inter-diffusion
更新于2025-09-19 17:13:59
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Laser Molecular Beam Epitaxy (LMBE) Technique grown GaN p-n junction
摘要： Gallium Nitride (GaN) thin films have been prepared using Laser Molecular Beam Epitaxy (LMBE) technique at moderate growth temperature in N2 gas ambience. The structural and optical properties of the films were optimized. A p-n junction diode has been successfully realised using GaN film grown by UHV-LMBE technique and p-type Mg:GaN/Sapphire substrate. Rectifying diode characteristics with low knee voltage of 1.2V were obtained for the prepared p-n junction, highlighting the promising prospects of employing LMBE technique for the realization of GaN based LEDs.
关键词： Gallium Nitride,Laser MBE,p-n heterojunction
更新于2025-09-16 10:30:52
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Indium antimonide photovoltaic cells for near-field thermophotovoltaics
摘要： Indium antimonide photovoltaic cells are specifically designed and fabricated for use in a near-field thermophotovoltaic device demonstrator. The optimum conditions for growing the p-n junction stack of the cell by means of solid-source molecular beam epitaxy are investigated. Then processing of circular micron-sized mesa structures, including passivation of the side walls, is described. The resulting photovoltaic cells, cooled down to around 77 K in order to operate optimally, exhibit excellent performances in the dark and under far-field illumination by thermal sources in the [600–1000] °C temperature range. A short-circuit current beyond 10 μA, open-circuit voltage reaching almost 85 mV, fill factor of 0.64 and electrical power at the maximum power point larger than 0.5 μW are measured for the cell with the largest mesa diameter under the highest illumination. These results demonstrate that these photovoltaic cells will be suitable for measuring a near-field enhancement of the generated electrical power.
关键词： MBE,Passivation,Thermophotovoltaics,InSb
更新于2025-09-16 10:30:52
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Synthesis of Monolayer Blue Phosphorus Enabled by Silicon Intercalation
摘要： The growth of entirely synthetic two-dimensional (2D) materials could further expand the library of naturally occurring layered solids and provide opportunities to design materials with finely tunable properties. Among them, the synthesis of elemental 2D materials is of particular interest as they represent the chemically simplest case and serve as model system for exploring the on-surface synthesis mechanism. Here, a pure atomically-thin blue phosphorous (BlueP) monolayer is synthesized via silicon intercalation of the BlueP-Au alloy on Au(111). The intercalation process is characterized at the atomic scale by low-temperature scanning probe microscopy, and further corroborated by synchrotron radiation-based x-ray photoelectron spectroscopy measurements. The evolution of the band structures from BlueP-Au alloy into Si intercalated BlueP are clearly revealed by angle-resolved photoemission spectroscopy and further verified by density functional theory calculations.
关键词： MBE,STM,Si intercalation,monolayer blue phosphorus,ARPES
更新于2025-09-16 10:30:52
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Lasing of a Quantum-Cascade Laser with a Thin Upper Cladding
摘要： We present the results of experiments on the fabrication and study of the properties of quantum-cascade lasers of the spectral range of 7–8 μ m in the geometry of a waveguide with a thin top cladding based on indium phosphide. The heterostructure is synthesized by molecular beam epitaxy on an InP substrate with an active region based on a heteropair of In0.53Ga0.47As/Al0.48In0.52As solid alloys. Laser emission at a wavelength of 7.8 μ m at a temperature of 300 K with a threshold current density of ~6 kA/cm2 was achieved. The values of characteristic temperatures T0 and T1 for the studied quantum-cascade lasers are of the order of 150 and 450 K, respectively. The results obtained confirm that the design of the waveguide with a thin top cladding for devices for detecting liquids, the fabrication of microfluidic devices, and photonic circuits on silicon holds promise.
关键词： quantum-cascade laser,indium phosphide,lasing,MBE
更新于2025-09-12 10:27:22
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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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The Growth of GeSn Layer on Patterned Si Substrate by MBE Method
摘要： A method to grow high quality GeSn alloy strips with assistance of Sn has been developed, and strips grow laterally on Si(111) substrates in molecular beam epitaxy (MBE) chamber. The GeSn heteroepitaxial strip has been proven to be of good crystalline quality without threading dislocations (TDs) by transmission electron microscopy (TEM). In the meantime, introduction of Sn into Ge was investigated by Raman spectra and energy-dispersive X-ray spectroscopy (EDS). In addition, size and density of GeSn strip can be adjusted by changing the growth conditions, and Sn concentration varies approximately linearly against the epitaxial temperature. Moreover, the Hall mobility of GeSn alloy strips at room temperature was 336 cm2·V-1·s-1 and the carrier concentration was 7.9×1012 cm?3 by Hall measurement. Therefore, the proposed method provides an easy technique to grow high quality GeSn materials for Si-based photonics and microelectronics applications.
关键词： GeSn alloy,microelectronics,photonics,MBE,Si substrate
更新于2025-09-11 14:15:04
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Study on Al <sub/>2</sub> O <sub/>3</sub> /Ge interface formed by ALD directly on epitaxial Ge
摘要： Germanium (Ge) has been attracting considerable attention as a high mobility channel material to enhance the performance of CMOS circuits. One of the most important issues for realization of practical Ge-MOSFET devices with superior performances is requirement to improve qualities of gate dielectric/Ge interfaces. In this work, Al2O3/Ge structures are fabricated by direct atomic layer deposition (ALD) on epitaxialy grown Ge. We indicate that ALD incubation time is fully suppressed by the ALD on a completely clean Ge surface created by Ge epitaxy on a Ge substrate. Moreover, x-ray photoelectron spectroscopy analyses reveal that unintentional formation of a GeO2 at the Al2O3/Ge interface can be almost avoided by the ALD on the epitaxial Ge whereas the interfacial GeO2 layer is present for samples exposed to the air before ALD. These results clearly indicate that direct ALD on epitaxial Ge is a very promising method to signi?cantly improve Ge MOSFET performances.
关键词： Germanium,XPS,Al2O3,ALD,MBE
更新于2025-09-09 09:28:46
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Gallium Oxide || MBE growth and characterization of gallium oxide
摘要： Gallium oxide (Ga2O3) is an ultrawide bandgap (UWBG) oxide semiconductor with an indirect bandgap of 4.5–5.2 eV. The beta-phase (β-Ga2O3) is the commonly regarded as most stable of the several crystalline phases (or polymorphs) of Ga2O3. Because of its wide bandgap, it is transparent from ultraviolet to visible wavelengths. It had first been widely explored as a transparent conductive oxide (TCO) for optical devices such as light-emitting diodes. Also, it has been used as a gate dielectric in metal oxide semiconductor (MOS) structures in GaAs. The β-Ga2O3 can be synthesized by melt growth techniques such as Czochraski, floating zone (FZ), and edge-defined film-fed growth (EFG) at atmospheric pressure which can provide inexpensive large area bulk substrates. The commercial availability of large area Ga2O3 substrates is an important advantage over GaN and similar group III-N compound semiconductors in many potential electrical and optical device applications. Besides material benefit of UWBG, these substrates provide a high-quality crystalline platform for power electronics devices that require higher crystalline quality, low-defect density material with precise doping control capabilities.
关键词： β-Ga2O3,MBE growth,Gallium oxide,ultrawide bandgap,heteroepitaxy,homoepitaxy
更新于2025-09-09 09:28:46