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Structural, morphological, optical and electrical characterization of InGaN/GaN MQW structures for optoelectronic applications
摘要： InGaN/GaN Multiple Quantum Well (MQW) structures were grown on c-plane sapphire substrate using metal organic chemical vapour deposition technique by varying the MQW periods. The indium composition and thickness were estimated using high-resolution X-ray diffraction. InGaN well, GaN barriers and Indium composition were estimated as 3 nm, 18 nm and 16-18% using epitaxy smooth fit software. Reciprocal space mapping revealed that InGaN/GaN MQW samples were coherently strained. High-resolution transmission electron microscopy and scanning electron microscopy exhibit decrease in the surface roughness with increase in the number of InGaN/GaN MQW periods with respect to the number of defects comprising of threading dislocations and hexagonal V-pits. Self-organized In(Ga)N like nanostructures with spiral growth mechanism was also observed due to the low temperature growth of p-GaN layer. The photoluminescence spectra of the MQWs showed a red-shift when the number of QW periods was increased due to quantum confined stark effect. Hall Effect microscopy images confirmed good interface between the InGaN/GaN MQW structures. Atomic force microscopy and scanning electron microscopy exhibit decrease in the surface roughness measurement displayed good semiconducting behavior in the InGaN/GaN MQW structures. The carrier concentration values also emphasized adequate variations when number of periods was increased.
关键词： V-pits,InGaN,Photoluminescence,Multiple Quantum Well,nanostructures
更新于2025-11-21 11:18:25
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Electrochemical capacitance-voltage profiling of nonuniformly doped GaAs heterostructures with SQWs and MQWs for LED applications
摘要： Light-emitting heterostructures with single and multiple GaAs/InGaAs quantum wells have been investigated by means of electrochemical capacitance-voltage (ECV) profiling. Capacitance-voltage characteristics were measured; concentration profiles of free charge carriers over the heterostructure depth as well as the intensity of quantum well filling by charge carriers were obtained. In heterostructures with a single quantum well (QW) we considered limitations of capacitance techniques for undoped QW profiling, which is situated near the metallurgic border of the p–n –junction. We made a detailed consideration of phenomena related to Debye smearing and we developed and analyzed the dependence of the space charge region width on the doping. Special attention was paid to investigation of the “blind” area. This was inspired by the practical problem from capacitance spectroscopy of semiconductors, when the researcher poses the task of obtaining a free charge carrier depth distribution profile as deep as possible in the space charge region, i.e. where the intensity of the electric field is maximum. Generally, the active QW of a LED heterostructure is placed deep in the space charge region, so reaching these regions is extremely important for practical problems. We present an evolution of capacitance-voltage characteristics during ECV profiling of nonuniformly doped p – n– heterostructures. For a heterostructure with multiple quantum wells we registered a response from 6 QWs.
关键词： capacitance-voltage profiling,heterostructure,quantum well,nonuniform doping,Electrochemical capacitance-voltage profiling,quantum dot,light-emitting diodes
更新于2025-11-14 17:28:48
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Influence of the position dependent effective mass on the nonlinear optical properties in semiparabolic and parabolic quantum well with applied magnetic field
摘要： In the current work, the nonlinear optical properties in GaAs/Ga1?xAlxAs semiparabolic and parabolic quantum well(QW) with constant effective mass(CEM) and position dependent effective mass(PDEM) are estimated for different applied magnetic field. In this regard, we have obtained the analytical expressions of the nonlinear rectification(OR), second harmonic generation(SHG), third harmonic generation(THG), optical absorption coefficients(OACs), and refractive index changes(RICs) by using the compact density matrix formalism. Simultaneously, we obtain the reliable energy eigenvalues and their corresponding eigenfunctions via the finite difference method. According to the obtained results, it is found that: (1)the correct inclusion of PDEM is the cause of a noticeable difference in nonlinear optical properties with respect to the use of CEM. (2)the applied magnetic field bear substantial technological importance in the process of nonlinear optical properties modulation.
关键词： Quantum well,Magnetic field,Position dependent effective mass,Optical properties
更新于2025-09-23 15:23:52
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Investigation of RF and DC Performance of E-Mode In <sub/>0.80</sub> Ga <sub/>0.20</sub> As/InAs/In <sub/>0.80</sub> Ga <sub/>0.20</sub> as Channel based DG-HEMTs for Future Submillimetre Wave and THz Applications
摘要： In this paper, we systematically investigated the DC and RF behaviour of the novel Enhancement-Mode (E-Mode) Double-Gate High Electron Mobility Transistors (DGHEMTs) using Sentaurus-TCAD software. The scalability of the novel DGHEMT is also studied by analysing the short channel effects. The attractive features of the proposed DGHEMT are intrinsic In0.80Ga0.20As/InAs/In0.80Ga0.20As channel, dual silicon delta doping sheets and platinum (Pt) buried gate technology. The proposed DGHEMT with Lg = 20 nm exhibits a gm_max of 3970 mS/mm and IDS_max of 1650 mA/mm at VGS = 0.6 V and VDS = 0.8 V. The proposed DGHEMT exhibits a threshold voltage of 20 mV which indicates its E-Mode behaviour. The sub-threshold swing (SS) and DIBL values obtained for Lg = 20 nm DGHEMT at VDS = 0.5 V are 74 mV/dec and 78 mV/V respectively. The Lg = 20 nm proposed E-Mode DGHEMT also exhibit a fT and fmax of 826 and 1615 GHz respectively at VDS = 0.6 V. The computed logic gate delay for the Lg = 20 nm DGHEMT is 31.25 fS with an electron velocity under the gate of 6.4 × 107 cm/S. This excellent RF and DC behaviour of the proposed DGHEMT makes them an excellent choice for future sub-millimetre wave and THz frequency applications.
关键词： quantum well (QW),InAs,Drain induced barrier lowering (DIBL),short channel effects (SCEs),gate delay,sub-threshold swing (SS)
更新于2025-09-23 15:23:52
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‘Forbidden’ intersubband optical transitions in quantum well structures in a tilted magnetic field
摘要： In this paper, we report on the behavior of intersubband optical absorption and emission spectrum in quantum well structures with an asymmetrical potential profile in a quantizing magnetic field tilted with respect to the layers in the considered structure. The analysis of the effect of both the magnetic field value and orientation and potential profile of a quantum well structure on the intensity of the 'forbidden' (Δn ≠ 0) intersubband optical transitions is presented. We also present the approximate analytical expression for the estimation of the contribution to the absorption/emission coefficient of intersubband transitions with different Δn.
关键词： intersubband optical transitions,Landau levels,quantum well structures
更新于2025-09-23 15:23:52
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Design of InP Based High Speed Photodiode for 2 μm Wavelength Application
摘要： In this paper, we proposed and designed the high speed uni-traveling carrier photodiodes operating beyond 2 μm. InGaAs/GaAsSb type-II multiple quantum wells (MQWs) were used as the absorption region of uni-traveling carrier photodiode to have optical response beyond 2 μm. A rate equation model was developed to study the bandwidth characteristics of this photodiode. The carrier dynamics of the carrier sweeping out process was discussed, and the structure parameters of the quantum wells were optimized. Result shows a 3-dB bandwidth over 40 GHz can be achieved with the optimized design. We also studied the feasibility of dual depletion PIN (DD-PIN) photodiode with MQWs absorber. The optimized DD-PIN photodiode could achieve similar bandwidth under relatively high-bias condition.
关键词： high speed photodiodes,type-II quantum well,Carrier dynamic,uni-traveling carrier photodiode
更新于2025-09-23 15:22:29
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Photodetachment of Au- ion confined in a quantum well
摘要： We investigate the single channel photodetachment dynamics of non-hydrogenic negative ion confined in a quantum well for the first time. We choose Au- ion as an example and put forward an analytical formula for the photodetachment cross section using both the quantum mechanical method and the semiclassical closed orbit theory. It is found that the photodetachment cross section of Au- ion in a quantum well can be written as a smooth background term multiply by a modulation factor. The calculation results suggest that multi-periodic oscillatory structures appear in the photodetachment cross section, and the oscillating pattern depends on the position of the ion in the quantum well and the laser light polarization sensitively. We compare the results calculated using the quantum mechanical method and the closed orbit theory, and find good agreement between the two results. The photodetachment cross section formula we put forward is universal, and can be applied to any negative ion with a p-wave photodetachment. On account of its general applicability, our work can provide some guidance for the experimental study of the photodetachment processes of non-hydrogenic negative ions in the presence of a quantum well or a microcavity.
关键词： quantum well,Au- ion,Photodetachment
更新于2025-09-23 15:22:29
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Strain-optoelectronic coupling properties of externally deformed nanoribbons with embedded quantum well
摘要： Strain-engineering provides a critical mechanism for tuning the band structure of quantum wells (QWs). However, due to the inherent rigidity of the semiconductor materials, the strain induced by lattice-mismatch is restricted to be invariable, uniform, thus cannot be subject to direct mechanical loading processes. Therefore, the flexible nanoribbons (NRs) in a variety of configurations offer entirely new research perspectives in modulation of the optoelectronic characteristic of QWs by curvature-induced inhomogeneous strain. In this paper, we propose a strategy to fabricate the QW layer embedded in uniaxially wavy NRs. To thoroughly figure out the internal strain-optoelectronic coupling mechanism, we establish a simple and accurate calculation model for externally deformed QW NRs using the eight-band k·p perturbation method for the first time. Luttinger-Kohn-Pikus-Bir Hamiltonian (LKPBH) for strained semiconductor is adopted and solved by finite-difference method (FDM). Theoretical calculations reveal inclined band edges, which result in the quantum-confined stark effect (QCSE) in the bended QW NRs. Continuously and periodically varied band gap of the wavy QW is revealed with a blue-shift from peak to valley of the sample NR, which agrees well with the μ-photoluminescence measurements. Further adjustments of the external configuration are explored to study the impact of the larger deformed structure on the curvature and band gap of the wavy QW within the confinement of the fracture limit.
关键词： nanoribbons,optoelectronic,strain,k·p method,quantum well
更新于2025-09-23 15:22:29
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Optical Properties and Carrier Transport in a Biased GaAs/AlAs Asymmetric Quintuple-Quantum-Well Superlattice
摘要： Photoluminescence (PL) properties and carrier transport in a GaAs/AlAs asymmetric quintuple-quantum well superlattice (AQQW-SL) were investigated. Since AQQWs are separated by very thin AlAs barriers, various carrier transport phenomena are expected due to the strong coupling of wave functions between the Γ states in the GaAs QWs and the X states in the AlAs barriers. A 20-period AQQW was embedded in the i-layer of a pin diode. A PL signal between the ground Γ and the heavy hole (hh) states was observed around 740 nm. However, another PL branch was observed at about 665 nm around 6 V. Based on the numerical calculation of the Γ and X wave functions, the electron transport from the X state in the thick AlAs barrier (X11) to the Γ state in the third QW (Γ31) occurs at 6.1 V. Thus, a PL signal at 665 nm can be attributed to the recombination between Γ31 and hh11.
关键词： GaAs/AlAs,photoluminescence,asymmetric quintuple-quantum-well,superlattices
更新于2025-09-23 15:22:29
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V-Defect and Dislocation Analysis in InGaN Multiple Quantum Wells on Patterned Sapphire Substrate
摘要： InGaN/GaN multiquantum well (MQW) structures have been grown on cone-shaped patterned sapphire substrates (CPSS) by metalorganic chemical vapor deposition (MOCVD). From the transmission electron microscopy (TEM) results, we found that most of the threading dislocations (TDs) in the trench region of the CPSS were bent by lateral growth mode. Also the staircase-like TDs were observed near the slant region of the cone pattern, they converged at the slope of the cone patterned region by staircase-upward propagation, which seems to effectively prevent TDs from vertical propagation in the trench region. The associated dislocation runs up into the overgrown GaN layer and MQW, and some (a+c) dislocations were shown to decompose inside the multi-quantum well, giving rise to a misfit segment in the c-plane and a V-shape defect. From cross-sectional TEM, we found that all V defects are not always connected with TDs at their bottom, some V defects are generated from the stacking mismatch boundaries induced by stacking faults which are formed within the MQW due to the strain relaxation.
关键词： V defects,Transmission electron microscopy (TEM),InGaN multi-quantum well (MQW),Threading dislocations (TDs)
更新于2025-09-23 15:22:29