||廣田正樹, 自動車関連MEMSを中心とするICT技術動向, MEMS Market Agenda for 2020, 2017.10, 自動車は、MEMSセンサを利用した電子制御システムにより、排出ガス規制への対応、燃料消費量の低減、交通事故の減少など社会からの要請へ答えてきた。今後、燃費規制の強化や自動運転の普及拡大によりMEMS技術およびICT技術の重要性が増すと考えられる。本発表では、これまでの事例と今後の展望について紹介する。.
||masaki Hirota, Shiichi Iio, Yoshimi Ohta, Yuusuke Niwa, Tomoyuki Miyamoto, Wireless power transmission between a NIR VCSEL array and silicon solar cells, 20th Microoptics Conference, MOC 2015, 2015.10, Aiming widespread use of wireless power transmission, optical wireless power transmission at wavelength of 975 nm between vertical cavity surface emitting laser (VCSEL) arrays and a single crystalline Si solar cell was studied. The power generation efficiency of the cell was measured as high as 33% which was higher than the efficiency of 18% at the time of irradiation with sunlight. This is because the transmission loss is mainly eliminated. However, further reduction of the electrical resistance of the solar cell is necessary because the efficiency decreases with increasing incident energy..
||Yasuyoshi Kurokawa, Yuya Watanabe, Shinya Kato, Yasuharu Yamada, Akira Yamada, Yoshimi Ohta, Yusuke Niwa, masaki Hirota, Observation of light scattering properties of silicon nanowire arrays, 39th IEEE Photovoltaic Specialists Conference, PVSC 2013, 2013.01, Silicon nanowire (SiNW) arrays were pre metal assisted chemical etching (MAE) method for the ap to solar cells. The SiNW arrays were mechanically peeled the Si substrate to obtain the optical properties of SiNW themselves. The absorptance of the SiNW array with the 10 μm is much higher than theoretical absorptance of 10 flat Si wafer. The angular distribution function (transmittance of SiNW arrays was also measured. It was that the Mie-related scattering plays an important ro strong optical confinement of the SiNW arrays..
||Yasuyoshi Kurokawa, Shinya Kato, Yuya Watanabe, Akira Yamada, Makoto Konagai, Yoshimi Ohta, Yusuke Niwa, masaki Hirota, Effect of the quantum size effect on the performance of solar cells with a silicon nanouwire array embedded in SiO2, 2012 MRS Spring Meeting, 2012.12, The electrical characteristics of silicon nanowire (SiNW) solar cells with p-type hydrogenated amorphous silicon oxide (Eg=1.9 eV)/n-type SiNWs embedded in SiO2/n-type hydrogenated amorphous silicon (E g=1.7 eV) structure have been investigated using a two-dimensional device simulator with taking the quantum size effects into account. The average bandgap of a SiNW embedded in SiO2 increased from 1.15 eV to 2.71 eV with decreasing the diameter from 10 nm to 1 nm due to the quantum size effect. It should be noted that under the sunlight with AM1.5G the open-circuit voltage (Voc) of SiNW solar cells also increased to 1.54 V with decreasing the diameter of the SiNWs to 1 nm. This result suggests that it is possible to enhance the Voc by the quantum size effect and a SiNW is a promising material for the all silicon tandem solar cells..
||Shinya Kato, Yuya Watanabe, Yasuyoshi Kurokawa, Akira Yamada, Yoshimi Ohta, Yusuke Niwa, masaki Hirota, Influence of surface recombination on the performance of SiNW solar cells and the preparation of a passivation film, 2012 MRS Fall Meeting, 2012.01, Al2O3 was deposited on silicon nanowire (SiNW) arrays by atomic layer deposition (ALD) as a passivation layer to reduce surface recombination velocity. As a result, effective minority carrier lifetime was improved from 1.82 to 26.2 μs. From this result, the relative low-surface recombination rate of 2.73 cm/s was obtained from a calculation using one-dimensional device simulation (PC1D). The performance of SiNW solar cells was also simulated by considering the surface recombination velocity on the side of SiNWs using two-dimensional device simulation. It was found that Al 2O3 deposited by ALD can improve open-circuit voltage of SiNW solar cells even if the structure has a high-aspect ratio and large surface area. Therefore, improvement in the performance of SiNW solar cells can be expected..
||masaki Hirota, Yoshimi Ohta, Yasuhiro Fukuyama, Masafumi Tsuji, Masanori Saito, Thermal imaging technology using a thermoelectric infrared sensor, 2008 SAE World Congress, 2008.04, This paper describes a low-cost 48 × 48 element thermal imaging camera intended for use in measuring the temperature in a car interior for advanced air conditioning systems. The compact camera measures 46 × 46 × 60 mm. It operates under a program stored in the central processing unit and can measure the interior temperature distribution with an accuracy of ±0.7°C in range from 0 to 40°C. The camera includes a thermoelectric focal plane array (FPA) housed in a low-cost vacuum-sealed package. The FPA is fabricated with the conventional IC manufacturing process and micromachining technology. The chip is 6.5 × 6.5 mm in size and achieves high sensitivity of 4,300 V/W, which is higher than the performance reported for any other thermopile. This high performance has been achieved by optimizing the sensor's thermal isolation structure and a precisely patterned Au-black absorber that attains high infrared absorptivity of more than 90%. The package incorporates a wide-angle zinc sulfide (ZnS) lens that is fabricated using moulding technology. The field of view is 60 deg. by 60 deg. The performance of the sensor is suitable for measuring car interior temperatures..
||masaki Hirota, Yoshimi Ohta, Yasuhiro Fukuyama, Low-cost thermo-electric infrared FPAs and their automotive applications, Infrared Technology and Applications XXXIV, 2008.06, This paper describes three low-cost infrared focal plane arrays (FPAs) having a 1,536, 2,304, and 10,800 elements and experimental vehicle systems. They have a low-cost potential because each element consists of p-n polysilicon thermocouples, which allows the use of low-cost ultra-fine micro-fabrication technology commonly employed in the conventional semiconductor manufacturing processes. To increase the responsivity of FPA, we have developed a precisely patterned Au-black absorber that has high infrared absorptivity of more than 90%. The FPA having a 2,304 elements achieved high resposivity of 4,300 V/W. In order to reduce package cost, we developed a vacuum-sealed package integrated with a molded ZnS lens. The camera aiming the temperature measurement of a passenger cabin is compact and light weight devices that measures 45 × 45 × 30 mm and weighs 190 g. The camera achieves a noise equivalent temperature deviation (NETD) of less than 0.7°C from 0 to 40°C. In this paper, we also present a several experimental systems that use infrared cameras. One experimental system is a blind spot pedestrian warning system that employs four infrared cameras. It can detect the infrared radiation emitted from a human body and alerts the driver when a pedestrian is in a blind spot. The system can also prevent the vehicle from moving in the direction of the pedestrian. Another system uses a visible-light camera and infrared sensors to detect the presence of a pedestrian in a rear blind spot and alerts the driver. The third system is a new type of human-machine interface system that enables the driver to control the car's audio system without letting go of the steering wheel. Uncooled infrared cameras are still costly, which limits their automotive use to high-end luxury cars at present. To promote widespread use of IR imaging sensors on vehicles, we need to reduce their cost further..
||Kofi A A Makinwa, Herman Casier, Ir Jakob Jongsma, masaki Hirota, Bernhard Jakoby, Bill Clark, Sensors on the move, 2006 IEEE International Solid-State Circuits Conference, ISSCC, 2006.02.
||T. Matsushita, T. Mihara, H. Ikeda, masaki Hirota, Y. Hirota, Intelligent power device having large immunity from transients in automotive applications, Proceedings of the 2nd International Symposium on Power Semiconductor Devices and ICs - ISPSD '90, 1990.12, A novel IPD (intelligent power device) technology for an automotive high-side switch has been developed which is applicable to devices up to the 60-V range. The fabrication process includes only one-time epitaxial growth. A new vertical DMOS FET with built-in cellular Zener diodes has also been developed. The avalanche capability of the DMOS is about 10 times greater than that of the conventional one. The control circuits of the developed IPD are protected against battery line transients by a 60-V Zener diode between the VDD and VSS terminals and two voltage limiters..