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On Optimising Spatial Sampling Plans for Wafer Profile Reconstruction ? ?The second author gratefully acknowledges the financial support provided by Irish Manufacturing Research (IMR) for this research.
摘要： Wafer metrology is an expensive and time consuming activity in semiconductor manufacturing, but is essential to support advanced process control, predictive maintenance and other quality assurance functions. Keeping metrology to a minimum is therefore desirable. In the context of spatial sampling of wafers this has motivated the development of a number of data driven methodologies for optimizing wafer sampling plans. Two such methodologies are considered in this paper. The first combines Principal Component Analysis and Minimum Variance Estimation (PCA-MVE) to determine an optimum subset of sites from historical metrology data from a larger candidate set, while the second employs Forward Selection Component Analysis (FSCA), an unsupervised variable selection technique, to achieve the same result. We investigate the relationship between these two approaches and show that under specific conditions a regularized extension of FSCA, denoted FSCA-R, and PCA-MVE are equivalent. Numerical studies using simulated data verify the equivalence conditions. Results for simulated and industrial case studies show that the improvement in wafer profile reconstruction accuracy with regularization is not statistically significant for the case studies considered, and that when PCA-MVE is implemented with a denoising step as originally proposed, it is outperformed by FSCA. Therefore, FSCA is the preferred methodology.
关键词： spatial sampling,Principal Component Analysis,Forward Selection Component Analysis,semiconductor manufacturing,wafer site selection,metrology
更新于2025-09-12 10:27:22
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Enhanced light-matter interaction in an atomically thin semiconductor coupled with dielectric nano-antennas
摘要： Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities having the optical mode volume close to or below the diffraction limit. Recently, it has become possible to make all-dielectric nano-cavities with reduced mode volumes and negligible non-radiative losses. Here, we realise low-loss high-refractive-index dielectric gallium phosphide (GaP) nano-antennas with small mode volumes coupled to atomic mono- and bilayers of WSe2. We observe a photoluminescence enhancement exceeding 104 compared with WSe2 placed on planar GaP, and trace its origin to a combination of enhancement of the spontaneous emission rate, favourable modification of the photoluminescence directionality and enhanced optical excitation efficiency. A further effect of the coupling is observed in the photoluminescence polarisation dependence and in the Raman scattering signal enhancement exceeding 103. Our findings reveal dielectric nano-antennas as a promising platform for engineering light-matter coupling in two-dimensional semiconductors.
关键词： atomically thin semiconductor,light-matter interaction,Raman scattering,dielectric nano-antennas,photoluminescence enhancement
更新于2025-09-12 10:27:22
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Low-Voltage AlGaAs/GaAs Thyristors as High-Peak-Current Pulse Switches for High-Power Semiconductor Laser Pumping
摘要： The dynamic characteristics of a low-voltage thyristor based on an AlGaAs/GaAs heterostructure have been studied in the mode of generation of high-amplitude pulses with width of tens of nanoseconds in a circuit with low-impedance load based on an array of high-power AlGaAs/GaAs semiconductor lasers. The presented approach uses thyristors and diode laser arrays as discrete components, so it can be extended to other (not AlGaAs/GaAs-based) semiconductor lasers. It is demonstrated that a current pulse can be generated with an amplitude of 69 A and a width of 40 ns in a vertically assembled stack of an array of semiconductor lasers and thyristors. It was shown that raising the number of single thyristors does not lead to pulse broadening and makes it possible to raise several-fold the peak current amplitude to 208 A, with the peak laser emission power reaching a value of 78 W.
关键词： heterostructure,Array of semiconductor lasers,laser diode (LD),thyristor
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 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) - Influence of Spacer Thickness on the Optical Properties of Vertically Stacked InP/AlGaInP Quantum Dot Lasers at the Short Wavelength
摘要： Quantum dot (QD) based semiconductor lasers are the widely used sources in many applications. The unique advantages are their low threshold current density, high characteristic temperature, and high differential material gain, owning to their discrete energy levels. The self-assembled InP QDs in the (AlxGa1?x)0.51In0.49P (AlxGaInP) barriers are of great interests due to the emitting spectrum from 630 nm to 780 nm [1]. However, limited by the low QD density, the low energy state density, and the small optical confinement factor, a single-sheet of QD only can provide a lower optical modal gain in the laser structure, which limits the laser performances. Meanwhile, the weak charge carrier confinement of the AlGaInP material further makes the devices sensitive to the operation temperature. One of the solutions for above issues is to increase the QD density by vertically stacking the QD layers. In the stacked QDs, the spacer thickness between the QD layers is one of the critical parameters needed to be carefully considered [2]. In this report, we investigated the influence of the spacer thickness on the optical properties of the vertically stacked InP/AlGaInP QD lasers at the emitting wavelength around 660 nm. The investigated laser structures (as shown in Fig. 1(a),) were grown by metal-organic vapor-phase epitaxy (MOVPE) on n-doped (100)-GaAs substrate oriented by 6° towards the [111]A direction. The epitaxial growth was performed at the temperature of 710°C and the pressure of 100 mbar with standard precursors. From bottom to top, the laser structure contains a 100 nm-thick GaAs:Si buffer layer, followed by a 50 nm-thick GaInP:Si layer and a 1 μm-thick AlInP:Si optical confinement layer. The InP quantum dot active region was grown and placed in the center of a 2×10 nm thick Al0.10GaInP barrier, surrounded by 2×150 nm Al0.55GaInP waveguide. The p-side layers are similar to the n-side, but the dopant was changed to Zinc. Here, we compared the optical properties of three different active region structures: single QD layer, double QD layers with the spacer of 6 nm and 10 nm. The measured electrically pumped modal absorption spectra of the investigated structures by the segmented contact method are shown in Fig. 1(b). It demonstrated that the thicker spacer introduces additional internal absorption loss due to the Al-based materials of the spacer. Meanwhile, the smaller spacer structure has the higher absorption of the large QD from the upper layer, attributed to the stronger strain effect and the increasing tunnelling rate. At room temperature, it demonstrates that the measured saturated peak net modal gain values (as shown in Fig. 1(c)) are 68.5 cm?1 and 57.8 cm?1 for the 6 nm-spacer structure and 10 nm-spacer structure, respectively, which are 1.56 and 1.32 times higher than the single-layer QD laser. The higher gain value of the smaller spacer structure is also attributed to the higher tunnelling probability and the shorter tunnelling time.
关键词： optical properties,InP/AlGaInP,spacer thickness,Quantum dot,semiconductor lasers
更新于2025-09-12 10:27:22
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Stark Shift of Hydrogenic and Non-Hydrogenic Donor Impurity Excited States in Parabolic Quantum Dot: Under the Effect of Electric Field and Temperature
摘要： In the present study, we discuss theoretically the influence of lateral and normal electric field on the hydrogenic donor impurity (HDI) and non-hydrogenic donor impurity (NHDI) excited state energies in a cylindrical quantum dot (CQD) with parabolic potential. The variational approach is employed to obtain the donor impurities ground and excited state energies in the framework of the effective mass approximation; consequently, the binding energy is calculated. The comparisons between the influence of the lateral and the normal electric fields on the Stark shift of the electron (ΔE1) and Stark shift of the HDI (ΔEimp) are given. It has been found that the direction of the electric field has a considerable effect on ΔEimp. Our results showed that ΔEimp has shown a blue shift for some HDI excited states and the other states showed a red shift. The results of the combined effect of the lateral electric field and the temperature on the HDI and NHDI binding energy have been presented. It has been indicated that the HDI states in small CQDs are very sensitive to the weak lateral electric field strength than both the normal electric field strength and the temperature values. More, the Stark shift in HDI ground state energy is more affected by the temperature in large CQDs than in small CQDs.
关键词： Hydrogenic Donor Impurity,Normal Electric Field,Semiconductor Quantum Dot,Lateral Electric Field,Excited State,Non-hydrogenic Donor Impurity
更新于2025-09-12 10:27:22
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[IEEE 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Fukuoka, Japan (2019.7.7-2019.7.11)] 2019 24th OptoElectronics and Communications Conference (OECC) and 2019 International Conference on Photonics in Switching and Computing (PSC) - Ultra High-Speed Quantum-Well Semiconductor Lasers for Data-Center and 5G-Wireless [Invited]
摘要： Evolution of ultra high-speed quantum-well semiconductor lasers (MQW-DMLs and MQW-EA/DFBs) with breakthrough technology for data-center and 5G-wireless are fully reviewed from pioneer research up to 100GbE/400GbE application, including challenge and advanced approaches for 800GbE and beyond.
关键词： Semiconductor lasers,Advanced Active Devices
更新于2025-09-12 10:27:22
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Effect of second-order nonlinearity on quantum coherent oscillations in a quantum dot embedded in a doubly resonant-semiconductor micro-cavity
摘要： The quantum Rabi oscillations in a coherently driven quantum dot embedded in a high-Q doubly resonant semiconductor micro-cavity in the presence of a strong second-order nonlinear medium is investigated theoretically. It is shown that the χ(2) nonlinearity effect the Rabi oscillations in a significant manner.
关键词： Rabi oscillation,Semiconductor microcavity,Second order nonlinearity
更新于2025-09-12 10:27:22
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Tuning the optical properties of CdSe quantum dot using graphene nanocomposite
摘要： Graphene semiconductor quantum dots (G-QDs) nanocomposites have attracted a lot of scienti?c interest. They have promising properties which allow them to be a good choice for photoelectric devices. G-QDs nanocomposites are prepared chemically by thermal decomposition of organometallic complex. Synthesis procedures were performed in the absence and presence of graphene in order to study its in?uence on the optical properties of the quantum dots (QDs) precisely. Various experimental techniques were utilized to study the morphology, crystal structure and the optical properties of the as-prepared materials using X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and UV/visible spectrophotometer. This paper will discuss the coupling between graphene and QDs showing the quenching of QDs emission, slowing rate of particle growth, increasing stock shift and enhancing the particle size distribution.
关键词： Semiconductor quantum dots,QDs emission,G-QDs nanocomposites
更新于2025-09-12 10:27:22
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Optical properties and electromagnetically induced grating in a hybrid semiconductor quantum dot-metallic nanorod system
摘要： An arti?cial molecule consisting of an SQD and an MNR embedded in 3D photonic crystal is proposed to realize EIG. Using the quantum mechanical density matrix approach, we have derived an expression of the absorption coe?cient in the SQD in presence of MNR. Nanoparticle geometry can modify the local ?elds that determine SQD-MNP coupling and to engineer the hybrid optical response. The probe absorption is reduced via a strong coupling ?eld, demonstrating spectral transparency window. It is worth noting that the background affects the relaxations of SQD. So, by making use of 3D photonic crystal as the background medium, reduced decay rate and consequently substantial local-?eld enhancement rate are provided. Based on EIT effect and a strong standing-wave ?eld, diffraction grating is achievable. The ?rst-order diffraction intensity can reach its maximum by tuning the system parameters. This model may be useful in designing new devices in all-optical communication.
关键词： Metallic nanorod (MNR),Semiconductor quantum dot (SQD),Electromagnetically induced grating (EIG),Photonic crystal (PC)
更新于2025-09-12 10:27:22