Keio University · Engineering
Professor Takaya Sugiura's research lab specializes in advanced semiconductor materials and devices, with a strong focus on energy-efficient and high-performance technologies for sustainable applications. The lab conducts cutting-edge research in crystalline silicon photovoltaics, including bifacial PERC solar cells and novel emitter structures, aiming to optimize efficiency and scalability. It also explores wide-bandgap semiconductors such as 4H-SiC and GaN for high-temperature and robust micro-electromechanical systems (MEMS) applications, particularly through piezoresistive effect characterization. The lab integrates numerical simulation and experimental validation to design next-generation energy harvesting and sensing devices.
Figures are computed from collected data and may differ slightly.
In recent years, Internet of Things (IoT) has become more and more important owing to the rapid expansion of the number of computing devices and data sizes. The evolution of IoT requires low-power and self-operating devices to expand the coverage area of computing resources. The main components of IoT are the large-scale integration (LSI) chips, which take the function of implementing the energy harvesters, control units and applications. They exhibit different physics or phenomena, making it di
We report on the evaluation of cell performances of the bifacial passivated emitter and rear cell (PERC) structures for both p- and n-type Cz-Si. We compared four conditions: Front-side illumination, with and without the rear metal contact, rear-side illumination, and double-side illumination. Furthermore, the effects of the rear contact area and the rear passivation surface recombination velocity (SRV) were evaluated. The numerical simulations were based on the experimental results of the p-typ
Abstract This study reviews the current methods of numerical simulations for crystalline‐Si (c‐Si) photovoltaic (PV) cells. The increased demand for PV devices has led to significant improvements in the performance of solar cell devices. The main contribution comes from c‐Si solar cells, which constitute 90% of the industry. Numerical analysis is effective for predicting, developing, and optimizing cell performances as the cell structures become more complex and include several parameters. Howev
The piezoresistive effect is characterized by the change in the resistivity of a material relative to mechanical forces exerted on it. Such materials can be used as pressure sensors and are among the most important components for micro-electro mechanical system applications. To date, most research on the piezoresistive effect has been directed toward cubic crystalline materials such as Si; however, the prospective non-cubic materials, such as SiC, are known to have exciting and promising propert
The diffusion profiles of the front floating emitter (FFE) and front surface field (FSF) in a bifacial interdigitated back contact solar cell are optimized. The optimization results revealed that the FFE and FSF schemes are beneficial for enhancing the cell performance at the front and rear sides, respectively. Lighter doping is particularly better for the FSF scheme, and the FFE scheme requires a large diffusion depth for improving the performance. Increasing the area of the rear emitter boosts
We examine the temperature dependence of the piezoresistive coefficients of silicon carbide (SiC) and gallium nitride (GaN) crystals, which are prospective materials for high-temperature applications owing to their wide-bandgap properties. The temperature-dependent piezoresistive coefficients of these materials were obtained by modeling experimental resistance changes using thermomechanical numerical simulations. This work reports the piezoresistive coefficients of 4H-SiC and GaN at the high-tem
Abstract Tunnel Oxide Passivated Contact (TOPCon) is a c-Si solar cell structure with tunneling oxide near the rear electrode. A full-area tunneling oxide provides sufficient passivation and low internal resistance with 1D carrier transport. Carrier tunneling mechanism is the key factor of a TOPCon solar cell; the thicker the tunneling oxide, the better is its ability to prevent minority-carrier tunneling. However, excessively thick oxide degrades majority-carrier tunneling. Therefore, the relat
The hole impact ionization coefficient (IIC) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML
This study presents the design of a novel on-chip photovoltaic device structure. The aim of this study is to avoid shading loss using a double ring structure. The proposed structure forms all contacts under shaded area; therefore, it is free from optical losses due to electrode shading. In addition, this design enhances integration by utilizing the photovoltaic cell space under the shading metals. This space can be used for interconnections or capacitors. The results indicate that the proposed s
We assessed the performance of transparent conductive oxide (TCO) materials for use in the heterojunction back contact + (HBC+) solar cell. In addition to indium tin oxide (ITO), titanium dioxide (TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and zinc oxide (ZnO) were evaluated as possible materials for the rear side of HBC+ solar cells. The results showed that the different optical and electrical parameters of the TCO materials affe
This study proposes a new ultraviolet-infrared (UV-Ir) compatible sensor fabricated using the standard CMOS process. The concept is verified through a numerical simulation, wherein the standard CMOS process parameters used are evaluated. The proposed sensor is an extension of a previously proposed RGB sensor designed on the standard CMOS process, and calculating the current ratio enables the detection of UV with high sensitivity. In addition, the use of current rectification eliminates the short
The field of piezoresistance has mainly advanced through experimental research; however, the improved accuracy of simulations and the emergence of new materials have increased the importance of simulations in this field. This review discusses the methods and current topics related to simulations of piezoresistive devices. Advancing simulation modeling will facilitate the computer-aided design of piezoresistive devices, and this review introduces the means of establishing these models by discussi
Gallium oxide (Ga2O3) attracts considerable technological interest because of its high Baliga’s figure-of-merit and high breakdown voltages. As the models for the breakdown behavior of n-doped Ga2O3 that consider soft (barrier lowering) and hard (avalanche effect) breakdowns are still lacking, in this study, we model the breakdown operations in &lt;001&gt; oriented Schottky barrier diodes considering both the soft- and hard-breakdown phenomena. The completion of the impact ionization mod
This article proposes an on- chip photovoltaic cell equipped with a tunnel oxide passivated contact (TOPCon) exhibiting selective carrier contact. The proposed structure utilizes the gate region as the TOPCon structure and performs best when the gate oxide is high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\kappa $ </tex-math></inline-formula> hafnium oxide (HfO2). Oxide thicknesses lower than 1.5 nm ena
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