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Controlling properties of GaN/dielectric interfaces is crucial for determining the characteristics of MOS-HEMT devices and their stability. Interface properties are largely affected by the techniques and specific conditions of dielectric deposition. In this work, a Taguchi design of experiment was applied to study the effect of plasma parameters during deposition of SiOx by PECVD for passivation of n-GaN. SiOx/GaN MIS capacitors were fabricated and characterized by capacitance measurement at a high probing frequency of 1 MHz. The interface states density, hysteresis and flatband voltage were analyzed and modeled in relation with the flow of SiH4, plasma power, chamber pressure and temperature. Excellent fits could be obtained on a single model including linear terms for all studied parameters and quadratic terms for the flow of SiH4 and temperature. We show that it is possible to obtain some control of the flatband voltage while maintaining a good interface quality. Positive flatband voltages are potentially of interest to enable normally-off operation for MOS-HEMTs and this could be obtained mainly by using a high SiH4/N2O ratio. To the contrary, negative flatband voltage values often ensure the most stable operation of MOS-HEMTs and this was achieved with a low SiH4/N2O and high plasma power. MIS capacitors with near-zero flatband voltage were also obtained with low SiH4/N2O ratio and low plasma power. Hysteresis and interface states density in relation with deposition plasma conditions are also analyzed in order to offer the best trade-offs depending on the end applications of MOS-GaN devices. By demonstrating the great impact of plasma conditions during dielectric deposition on electronic properties of MIS devices, we show that the process of gate insulation can be optimized to simultaneously control the density of defects and fixed charge at the interface.

This research paper delves into the potential use of solar energy as an alternative energy source for future vehicles. The study introduces a system that overcomes the limitations of traditional solar panels by achieving a reduced thickness of less than 35 mm, while acknowledging the challenges faced by vehicles, such as the inability to maintain a fixed orientation towards the sun and frequent shading from surrounding objects. To tackle these challenges, our system incorporates the design of an asymmetrical and extended polynomial lens and optimizes it to widen the acceptance angle of incident sunlight, enabling the solar panels to capture a wider range of solar radiation, even when the vehicle is not ideally aligned with the sun. The goal of this innovative design is not only to maximize energy output in urban conditions, ensuring efficient solar utilization despite shading challenges, but also to maintain a compact, lightweight structure suitable for installation on vehicle rooftops and competitive with ordinary PV panels. Additionally, our system is a tracking and heat spreader-free structure. This simple structure enables cheaper mass production and the lightweight nature of the structure results in affordable manufacturing and assembly processes. Through collaboration with micro-fabrication, macro-electronic industries, and micro-LED technologies, our system is a strong candidate for a low-cost, high-efficiency system. The results show an optical efficiency of around 52.53% for incident rays at a 45° angle, with the remaining rays captured by adjacent lenses resulting in a total optical efficiency around 76%.

The Versatile Video Coding (VVC) standard, finalized in 2020 by the Joint Video Experts Team (JVET) and the Video Coding Experts Group (VCEG), marks a major advancement in video compression technology, offering a 50% efficiency improvement over its predecessor, the High-Efficiency Video Coding (HEVC) standard. A key innovation in the VVC standard is the Quad Tree with nested Multi-Type Tree (QTMTT) structure, essential for the partitioning process. However, this enhancement has led to increased coding complexity, posing challenges for real-time applications. To address this, our paper focuses on optimizing the partitioning process in the VVC encoder under the Random Access (RA) configuration. We propose a novel approach that leverages inter-prediction by integrating both coding and motion information across inter-frames to enhance coding efficiency. This solution is implemented on the Fraunhofer Versatile Video Encoder (VVenC). It utilizes a set of lightweight Light Gradient Boosting Machine (LightGBM) binary classifiers to accurately predict the optimal split mode for each Coding Unit (CU). Consequently, our approach significantly accelerates the VVenC encoding process. Experimental results show that our method reduces the runtime of the slower preset by 43.21%, with only a slight bitrate increase of 2.9%. These improvements not only significantly reduce computational complexity but also outperform several existing state-of-the-art methods.

The recent progress in the fields of sensor miniaturization, light materials, automatic control, and battery management systems has opened up new opportunities for low-cost unmanned aerial vehicles (UAVs), such as quadrotors. In fact, quadrotors have transitioned from a primarily military application to being widely used almost everywhere. Evidently, controlling such robots requires a deep understanding of their dynamic behavior and the use of robust strategies to accomplish the flight missions without compromising users’ safety. This study presents a comprehensive survey of control strategies for unmanned quadrotors. In our examination, the performance assessment of widely used control algorithms is discussed. Furthermore, the concept of model-based design is presented as a solution for bridging the gap between simulation and experimental validation of control systems. It is anticipated that the present study will provide the reader with a clear vision of quadrotor UAV control theory.

Concentrated Photovoltaic (CPV) is a promising technology for higher efficiency power generation than other photovoltaic power generating technologies. However, the lack of demand and its failure in the commercial field is mainly due to its long-term reliability issues as well as its cost, which is an order of magnitude higher than the other technologies. Therefore, several measures have been taken to minimize the cost, improve the reliability as well as improve the performance of these concentrators. In this approach, Micro photovoltaic concentrators have been introduced as an outstanding alternative to shed light on all these challenges while keeping the same principle as the CPV modules. This paper presents a theoretical analysis of a micro photovoltaic concentrator system with a geometrical concentration ratio of 100x consisting of a Plano-convex lens as a primary optical element, a ball lens as a secondary optical element, and a solar cell. The aim is to present a compact module with high optical efficiency, low thermal stress, and high mechanical tolerance to keep the optimum optical alignment between the submillimeter cell and the small-sized optics.

This paper investigates the requirements, the feasibility and reliability of concentrator photovoltaic (CPV) with trackers in Fez city (Morocco) climate. In a first step, an appropriate sun tracker for a CPV prototype is design-simulated and then, based on finite element analysis, the effect of wind velocity distribution induced charge on the global structure (tracker and CPV module) is investigated for several elevation angle of the CPV unit. For all the investigated configurations, the maximum simulated misalignment still negligible, and is estimated to 4.6 × 10−6°, for a wind speed of 3.3 m/s. As a result, it is anticipated that the examined high CPV system (HCPV) will works safely under these effects. In a second step, using a home-developed Python code, and geometrical solar equations, calculations have been performed to estimate the diffuse, the direct and the global irradiations in this location. Ultimately, the energy performance of the system using System Advisor Model (SAM) software is carried out and compared to some on site real measurements. This simulation process led to a rigorous evaluation of the potential energy production with a tracked CPV panel, proving its viability in Fez Morocco. It also shows the level of accuracy of at least 0.5° that sun-tracking photovoltaic systems are necessary to maintain the least amount of power yield loss, especially for CPV facilities. This research will also serve as a valuable guide for the future sun-tracking CPV system.

Ultra-reliable low-latency communications, URLLC, are designed for applications such as self-driving cars and telesurgery requiring a response in milliseconds and are very sensitive to transmission errors. To match the computational complexity of LDPC decoding algorithms to URLLC applications on IoT devices having very limited computational resources, this paper presents a new parallel and low-latency software implementation of the LDPC decoder. First, a decoding algorithm optimization and a compact data structure are proposed. Next, a parallel software implementation is performed on ARM multicore platforms in order to evaluate the latency of the proposed optimization. The synthesis results highlight a reduction in the memory size requirement by 50% and a three-time speedup in terms of processing time when compared to previous software decoder implementations. The reached decoding latency on the parallel processing platform is 150 μs for 288 bits with a bit error ratio of 3.410–9.

This work deals with real conditions testing of two Fresnel lens-based optical concentrators for concentrator photovoltaic systems (CPV). Particular attention is paid to validate the performances of the secondary optical elements (SOEs), namely pyramid and cone, both made from highly transparent fused silica and mounted with a poly methyl methacrylate (PMMA) Fresnel lens as a primary optical element (POE). The effet of the focal distance of the POE on the main optical characteristics is analyzed by simulation and the corresponding results and behavior are discussed in details. Prototypes based on Fresnel lens having 75 and 100mm in diameter and pyramid- and cone-based secondary optical elements have been simulated, fabricated and tested. Optical and electrical characterization procedures are described in details. The optical efficiency, acceptance angle, spatial homogeneity of the output power and electrical performances of the fabricated CPV units are measured and are in a good agreement with simulation data. Results show that the pyramid-type concentrator gives the best optical and electrical performances. The electric efficiency achieved by the pyramid-based concentrators reaches 30% which make it able to reach the highest standards of CPV technology performances. A large acceptance angle of 1.35° is measured as one of the highest value reported in the literature for systems with pyramid as a SOE. A good agreement between simulation and experiment results has been obtained, confirming the performance expected from a CPV system having the same secondary optical element with a larger primary optical element.

Abstract Selective Area van der Waals Epitaxy (SAVWE) of III-Nitride device has been proposed recently by our group as an enabling solution for h-BN-based device transfer. By using a patterned dielectric mask with openings slightly larger than device sizes, pick-and-place of discrete LEDs onto flexible substrates was achieved. A more detailed study is needed to understand the effect of this selective area growth on material quality, device performance and device transfer. Here we present a study performed on two types of LEDs (those grown on h-BN on patterned and unpatterned sapphire) from the epitaxial growth to device performance and thermal dissipation measurements before and after transfer. Millimeter-size LEDs were transferred to aluminum tape and to silicon substrates by van der Waals liquid capillary bonding. It is shown that patterned samples lead to a better material quality as well as improved electrical and optical device performances. In addition, patterned structures allowed for a much better transfer yield to silicon substrates than unpatterned structures. We demonstrate that SAVWE, combined with either transfer processes to soft or rigid substrates, offers an efficient, robust and low-cost heterogenous integration capability of large-size devices to silicon for photonic and electronic applications.

Hybrid Concentrated Photovoltaics (HCPVs) are systems in which additional low-cost silicone solar cells are added to take advantage of the power generated by the diffuse radiation lost when using only multi-junction cells that work only with direct radiation. The work has been tested by simulating the performance of a hybrid CPV system composed of a Fresnel lens associated with a pyramid, multi junction cell as well as additional silicon solar cells. This proposal is compared with an ordinary CPV system and a system based on only silicon solar cells. The simulation results show that the CPV makes it possible to have a high optical efficiency of 94% at the pyramid exit for direct radiation, but this high efficiency rapidly decreases to 0% for diffuse radiation. In this case, the silicon solar cell comes into the scene to converts these diffused or non-concentrated rays into electricity, with an optical efficiency of 85%. It was also found that the Hybrid CPV system was able to increase the power by 21% compared to the CPV system.

The informed dynamic scheduling (IDS) strategies for the low-density parity check (LDPC) decoding have shown superior performance in error correction and convergence speed, particularly those based on reliability measures and residual belief propagation (RBP). However, the search for the most unreliable variable nodes and the residual precomputation required for each iteration of the IDS-LDPC increases the complexity of the decoding process which becomes more sequential, making it hard to exploit the parallelism of signal processing algorithms available in multicore platforms. To overcome this problem, a new, low-complexity scheduling system, called layered vicinal variable nodes scheduling (LWNS) is presented in this paper. With this LWNS, each variable node is updated by exchanging intrinsic information with all its associated control and variable nodes before moving to the next variable node updating. The proposed scheduling strategy is fixed by a preprocessing step of the parity control matrix instead of calculation of the residuals values and by computation of the most influential variable node instead the most unreliable metric. It also allows the parallel processing of independent Tanner graph subbranches identified and grouped in layers. Our simulation results show that the LWNS BP have an attractive convergence rate and better error correction performance with low complexity when compared to previous IDS decoders under the white Gaussian noise channel (AWGN).

In this paper, a robust flight control system is proposed for an autonomous quadrotor to quickly and accurately achieve the targeted trajectories. A novel supertwisting nonsingular terminal sliding mode control (STNTSMC) has been developed to ensure that the tracking errors vanish in a short finite-time. A nonlinear disturbance observer (DO) is incorporated into the control system to estimate the unknown external perturbations and to strengthen the system’s robustness. The Lyapunov theory is used to verify the closed-loop stability of the synthesized controller. Moreover, processor-in-the-loop (PIL) implementations are performed to validate the efficacy of the suggested method. The merit of the proposed DO-STNTSMC is evaluated under multiple flight scenarios. The obtained results demonstrate that the proposed controller has a highly reduced tracking error and strong robustness against random parameter changes and external disturbances, compared to conventional nonsingular terminal sliding mode control. Finally, experimental tests are conducted to validate the performance of the suggested method.

Reliable p-doped hexagonal boron nitride (h-BN) could enable wide bandgap optoelectronic devices such as deep ultra-violet light emitting diodes (UV LEDs), solar blind photodiodes and neutron detectors. We report the study of Mg in h-BN layers as well as Mg h-BN/AlGaN heterostructures. Mg incorporation in h-BN was studied under different biscyclopentadienyl-magnesium (Cp2Mg) molar flow rates. 2θ-ω x-ray diffraction scans clearly evidence a single peak, corresponding to the (002) reflection plane of h-BN with a full-width half maximum increasing with Mg incorporation in h-BN. For a large range of Cp2Mg molar flow rates, the surface of Mg doped h-BN layers exhibited characteristic pleats, confirming that Mg doped h-BN remains layered. Secondary ion mass spectrometry analysis showed Mg incorporation, up to 4 × 1018 /cm3 in h-BN. Electrical conductivity of Mg h-BN increased with increased Mg-doping. Heterostructures of Mg h-BN grown on n-type Al rich AlGaN (58% Al content) were made with the intent of forming a p-n heterojunction. The I-V characteristics revealed rectifying behavior for temperatures from 123 to 423 K. Under ultraviolet illumination, photocurrent was generated, as is typical for p-n diodes. C-V measurements evidence a built-in potential of 3.89 V. These encouraging results can indicate p-type behavior, opening a pathway for a new class of wide bandgap p-type layers.

The epitaxy of III-V semiconductors on silicon substrates remains challenging because of lattice parameter and material polarity differences. In this work, we report on the Metal Organic Chemical Vapor Deposition (MOCVD) and characterization of InAs/GaAs Quantum Dots (QDs) epitaxially grown on quasi-nominal 300 mm Ge/Si(001) and GaAs(001) substrates. QD properties were studied by Atomic Force Microscopy (AFM) and Photoluminescence (PL) spectroscopy. A wafer level µPL mapping of the entire 300 mm Ge/Si substrate shows the homogeneity of the three-stacked InAs QDs emitting at 1.30 ± 0.04 µm at room temperature. The correlation between PL spectroscopy and numerical modeling revealed, in accordance with transmission electron microscopy images, that buried QDs had a truncated pyramidal shape with base sides and heights around 29 and 4 nm, respectively. InAs QDs on Ge/Si substrate had the same shape as QDs on GaAs substrates, with a slightly increased size and reduced luminescence intensity. Our results suggest that 1.3 μm emitting InAs QDs quantum dots can be successfully grown on CMOS compatible Ge/Si substrates.

Concentrator Photovoltaic (CPV) technology, by using efficient optical elements, small sizes and high efficiency multi-junction solar cells, can be seen as a bright energy source to produce more cost-effective electricity. The main and basic idea is to replace the use of expensive solar cells with less expensive optical elements made from different materials. This paper aims to give to the readers a rapid and concise overview of CPV and the main characteristics to be considered when designing a CPV system. It reviews the main optical configurations presented in the literature, their advantages and drawbacks, as well as the recent progress in the concentration ratio and the major performances achieved in the field. The paper considers the more recent works, their optical designs, as well as their optical and electrical performances. It also relates the major achievements on the industrial side with the major milestones in CPV developments.

Object detection has been attracting much interest due to the wide spectrum of applications that use it. It has been driven by an increasing processing power available in software and hardware platforms. In this work we present a developed application for multiple objects detection based on OpenCV libraries. The complexity-related aspects that were considered in the object detection using cascade classifier are described. Furthermore, we discuss the profiling and porting of the application into an embedded platform and compare the results with those obtained on traditional platforms. The proposed application deals with real-time systems implementation and the results give a metric able to select where the cases of object detection applications may be more complex and where it may be simpler.