32 results on '"Yoshiharu Anda"'
Search Results
2. Comprehensive study on initial thermal oxidation of GaN(0001) surface and subsequent oxide growth in dry oxygen ambient.
- Author
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Takahiro Yamada, Joyo Ito, Ryohei Asahara, Kenta Watanabe, Mikito Nozaki, Satoshi Nakazawa, Yoshiharu Anda, Masahiro Ishida, Tetsuzo Ueda, Akitaka Yoshigoe, Takuji Hosoi, Takayoshi Shimura, and Heiji Watanabe
- Subjects
ELECTRIC properties of gallium nitride ,OXIDATION ,ROUGH surfaces ,GALLIUM nitride films ,X-ray photoelectron spectroscopy ,ATOMIC force microscopy - Abstract
Initial oxidation of gallium nitride (GaN) (0001) epilayers and subsequent growth of thermal oxides in dry oxygen ambient were investigated by means of x-ray photoelectron spectroscopy, spectroscopic ellipsometry, atomic force microscopy, and x-ray diffraction measurements. It was found that initial oxide formation tends to saturate at temperatures below 800 °C, whereas the selective growth of small oxide grains proceeds at dislocations in the epilayers, followed by noticeable grain growth, leading to a rough surface morphology at higher oxidation temperatures. This indicates that oxide growth and its morphology are crucially dependent on the defect density in the GaN epilayers. Structural characterizations also reveal that polycrystalline α- and β-phase Ga
2 O3 grains in an epitaxial relation with the GaN substrate are formed from the initial stage of the oxide growth. We propose a comprehensive model for GaNoxidation mediated by nitrogen removal and mass transport and discuss the model on the basis of experimental findings. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
3. Fast switching performance by 20 A / 730 V AlGaN/GaN MIS-HFET using AlON gate insulator
- Author
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Takahiro Yamada, Tsuguyasu Hatsuda, Hong-An Shih, Heiji Watanabe, Tetsuzo Ueda, Tamotsu Hashizume, Takuji Hosoi, Yoshiharu Anda, Mikito Nozaki, Naohiro Tsurumi, Takayoshi Shimura, and Satoshi Nakazawa
- Subjects
010302 applied physics ,Materials science ,business.industry ,Transistor ,chemistry.chemical_element ,Heterojunction ,High voltage ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,law.invention ,Hafnium ,Threshold voltage ,Hysteresis ,chemistry ,law ,0103 physical sciences ,Optoelectronics ,Breakdown voltage ,0210 nano-technology ,business - Abstract
In this paper, high current and high voltage AlGaN/GaN metal-insulator-semiconductor (MIS) heterojunction field-effect transistors (HFETs) on Si are demonstrated. The devices exhibit a drain current of 20 A as well as a breakdown voltage of 730 V, serving normally-off operations. Stable interfacial characteristics free from the hysteresis in the transfer characteristics are enabled by the introduction of AlON gate insulator. A recessed gate structure formed by epitaxial regrowth of AlGaN over the grooved AlGaN/GaN heterojunction successfully reduces the on-state resistance and eliminates the processing damage on the surface of the grooved structure. Note that an oxygen annealing followed by the deposition of AlON shifts the threshold voltage V th to positive side. The resultant switching performance by the 20 A / 730 V AlGaN/GaN MIS-HFET is very fast with dV/dt of 78 V/ns and 169 V/ns for turn-on and turn-off transitions, respectively, indicating that the proposed MIS-HFETs are very promising for practical power switching applications.
- Published
- 2017
4. A1W power consumption GaN-based isolated gate driver for a 1.0 MHz GaN power system
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Shuichi Nagai, Tsuguyasu Hatsuda, Osamu Tabata, Yasufumi Kawai, Songbek Che, Shingo Enomoto, Noboru Negoro, and Yoshiharu Anda
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Engineering ,business.industry ,020209 energy ,020208 electrical & electronic engineering ,Transistor ,Electrical engineering ,02 engineering and technology ,law.invention ,Electric power system ,law ,Power electronics ,Hardware_INTEGRATEDCIRCUITS ,0202 electrical engineering, electronic engineering, information engineering ,Gate driver ,Power semiconductor device ,Wireless power transfer ,Voltage source ,business ,Hardware_LOGICDESIGN ,Power density - Abstract
Fast switching operation of power electronics systems is significantly advantageous for reducing volume of passive components and increasing power density in the systems. Next generation power devices, such as GaN gate-injection transistor (GIT), are promising for high frequency operations and isolated gate driving is also highly recommended owing to its noise robustness. In this paper, we propose a GaN Hetero Junction Field-Effect Transistor (HFET)-based isolated gate driver for GaN power devices with Drive-by-Microwave (DBM) technology, which can provide very compact GaN-GIT power systems owing to a gate driving by a wireless power transfer without an additional isolated voltage source. The proposed DBM gate driver can drive GaN-GIT power devices at a high switching frequency of 3 MHz with relatively low power consumption (∼1 W) and provides a short propagation delay less than 20 nsec.
- Published
- 2017
5. Design and control of interface reaction between Al-based dielectrics and AlGaN layer for hysteresis-free AlGaN/GaN MOS-HFETs
- Author
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S. Nakazawa, M. Isliida, Mikito Nozaki, Heiji Watanabe, Akitaka Yoshigoe, Kenta Watanabe, Takayoshi Shimura, Takahiro Yamada, Takuji Hosoi, Yoshiharu Anda, and Tetsuzo Ueda
- Subjects
010302 applied physics ,Materials science ,business.industry ,Transistor ,Heterojunction ,Algan gan ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Hysteresis ,law ,0103 physical sciences ,Optoelectronics ,Process window ,Thermal stability ,0210 nano-technology ,business ,Layer (electronics) - Abstract
We have demonstrated hysteresis-free recessed gate AlGaN/GaN metal-oxide-semiconductor heterojunction field-effect transistor (MOS-HFET) by implementing AIGN gate insulator and selective AlGaN regrowth technique. High thermal stability and excellent electrical properties of AIGN gate dielectrics will provide a large process window for further optimization of AlGaN/GaN MOS-HFET.
- Published
- 2017
6. A Novel Thin Concentrator Photovoltaic With Microsolar Cells Directly Attached to a Lens Array
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Michael W. Wiemer, Daisuke Ueda, Daijiro Inoue, Tohru Nakagawa, Tetsuzo Ueda, Hidekazu Arase, Eiji Fujii, Inoue Kazuo, Tetsuya Asano, Hidetoshi Ishida, Akio Matsushita, Ryutaro Futakuchi, Akihiro Itou, Yoshiharu Anda, Masaki Yamamoto, Nobuhiko Hayashi, and Onur Fidaner
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Materials science ,business.industry ,Triple junction ,Photovoltaic system ,Heat sink ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Gallium arsenide ,Lens (optics) ,chemistry.chemical_compound ,Optics ,Cardinal point ,chemistry ,law ,Optoelectronics ,Fluidics ,Electrical and Electronic Engineering ,business ,Optical path length - Abstract
We propose a novel concept of thin and compact CPV modules in which submillimeter solar cells are directly attached to lens arrays without secondary optics or an extra heat sink. With this small cell size, the optical path length of the module can be brought down to one-twentieth that of conventional CPV modules. To achieve precise alignment of the microsolar cells at the lens focal points, we have developed a fluidic self-assembly technique that utilizes surface tension. This novel CPV module with triple junction microsolar cells demonstrated an efficiency of 34.7% under sunlight in the particular measured condition.
- Published
- 2014
7. Effects of post-deposition annealing in O2 on threshold voltage of Al2O3/AlGaN/GaN MOS heterojunction field-effect transistors
- Author
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Yoshiharu Anda, Tsunenobu Kimoto, Hong-An Shih, Naohiro Tsurumi, Tsuguyasu Hatsuda, Tetsuzo Ueda, Tamotsu Hashizume, and Satoshi Nakazawa
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010302 applied physics ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Annealing (metallurgy) ,Transistor ,General Engineering ,General Physics and Astronomy ,Algan gan ,Heterojunction ,01 natural sciences ,law.invention ,Threshold voltage ,law ,Fixed charge ,0103 physical sciences ,Oxygen plasma ,Optoelectronics ,Field-effect transistor ,business - Abstract
In this paper, we investigated the effects of the post-deposition annealing (PDA) on the threshold voltage (V th) of AlGaN/GaN MOS heterojunction field-effect transistors with atomic-layer-deposited Al2O3 using H2O vapor or oxygen plasma as the oxidant. By PDA, the V th shifts positively with the V th variations depending on the oxidants. The capacitance–voltage measurements reveal that the V th variation is attributed to the differences in the initial fixed charge density in the Al2O3 or/and the Al2O3/AlGaN for both oxidants.
- Published
- 2019
8. High-Voltage Isolation Technique Using Fe Ion Implantation for Monolithic Integration of AlGaN/GaN Transistors
- Author
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Tetsuzo Ueda, Yoshiharu Anda, Toshiyuki Takizawa, Tsuyoshi Tanaka, and Hidekazu Umeda
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Materials science ,business.industry ,Annealing (metallurgy) ,Transistor ,Wide-bandgap semiconductor ,High voltage ,Heterojunction ,Electronic, Optical and Magnetic Materials ,Ion ,law.invention ,Ion implantation ,law ,Electronic engineering ,Optoelectronics ,Breakdown voltage ,Electrical and Electronic Engineering ,business - Abstract
Ion implantation technique can be applied for planar isolation of AlGaN/GaN heterojunction field-effect transistors (HFETs), which enables high-density integration of the power switching transistors. So far, the reported isolation using ion implantation for GaN devices has never maintained high isolation voltages after high-temperature processing over 800 °C which is commonly used for the fabrication. In this paper, we present detailed analysis and mechanism of thermally stable isolation of GaN devices by Fe ion implantation keeping high breakdown voltage between the devices after high-temperature annealing. Ion species forming deep levels at atomic sites in GaN are examined by using first-principle calculation prior to the experiments. The calculation indicates that the Fe ions stay at Ga sites with deep levels in GaN. The following experiments using various ion species well agree with the aforementioned predictions, where implanted regions by other ions than Fe exhibit reduction of the resistivity after high-temperature annealing to recover the processing damage by the ion implantation. As a result, it is experimentally found that Fe is the only choice to serve high resistivity after the annealing. The Fe ion implantation enables high breakdown voltage of 900 V after the annealing at 1200 °C. This technique is indispensable to enable monolithic integration of the lateral AlGaN/GaN HFETs for high-voltage power switching systems.
- Published
- 2013
9. K-Band AlGaN/GaN MIS-HFET on Si with High Output Power over 10W
- Author
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Masayuki Kuroda, Yoshiharu Anda, Noboru Negoro, Hiroyuki Sakai, Masaaki Nishijima, Tetsuzo Ueda, Tomohiro Murata, and Tsuyoshi Tanaka
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Materials science ,Si substrate ,Power over ,business.industry ,K band ,Amplifier ,Optoelectronics ,Algan gan ,Electrical and Electronic Engineering ,business ,Electronic, Optical and Magnetic Materials - Published
- 2012
10. Physical and electrical characterizations of AlGaN/GaN MOS gate stacks with AlGaN surface oxidation treatment
- Author
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Takahiro Yamada, Satoshi Nakazawa, Tetsuzo Ueda, Akitaka Yoshigoe, Hong-An Shih, Takayoshi Shimura, Yoshiharu Anda, Takuji Hosoi, Mikito Nozaki, Heiji Watanabe, and Kenta Watanabe
- Subjects
010302 applied physics ,Thermal oxidation ,Materials science ,Physics and Astronomy (miscellaneous) ,Passivation ,business.industry ,General Engineering ,General Physics and Astronomy ,Synchrotron radiation ,chemistry.chemical_element ,Insulator (electricity) ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Grain growth ,chemistry ,X-ray photoelectron spectroscopy ,Aluminium ,0103 physical sciences ,Optoelectronics ,Electrical measurements ,0210 nano-technology ,business - Abstract
The impacts of inserting ultrathin oxides into insulator/AlGaN interfaces on their electrical properties were investigated to develop advanced AlGaN/GaN metal–oxide–semiconductor (MOS) gate stacks. For this purpose, the initial thermal oxidation of AlGaN surfaces in oxygen ambient was systematically studied by synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS) and atomic force microscopy (AFM). Our physical characterizations revealed that, when compared with GaN surfaces, aluminum addition promotes the initial oxidation of AlGaN surfaces at temperatures of around 400 °C, followed by smaller grain growth above 850 °C. Electrical measurements of AlGaN/GaN MOS capacitors also showed that, although excessive oxidation treatment of AlGaN surfaces over around 700 °C has an adverse effect, interface passivation with the initial oxidation of the AlGaN surfaces at temperatures ranging from 400 to 500 °C was proven to be beneficial for fabricating high-quality AlGaN/GaN MOS gate stacks.
- Published
- 2018
11. SiO2/AlON stacked gate dielectrics for AlGaN/GaN MOS heterojunction field-effect transistors
- Author
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Akitaka Yoshigoe, Takahiro Yamada, Kenta Watanabe, Takuji Hosoi, Masahiro Ishida, Takayoshi Shimura, Heiji Watanabe, Daiki Terashima, Mikito Nozaki, Tetsuzo Ueda, Yoshiharu Anda, and Satoshi Nakazawa
- Subjects
010302 applied physics ,Materials science ,Physics and Astronomy (miscellaneous) ,Dielectric strength ,business.industry ,Band gap ,General Engineering ,General Physics and Astronomy ,Heterojunction ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Capacitor ,law ,0103 physical sciences ,Optoelectronics ,Thermal stability ,Field-effect transistor ,0210 nano-technology ,business ,Layer (electronics) - Abstract
Stacked gate dielectrics consisting of wide bandgap SiO2 insulators and thin aluminum oxynitride (AlON) interlayers were systematically investigated in order to improve the performance and reliability of AlGaN/GaN metal–oxide–semiconductor (MOS) devices. A significantly reduced gate leakage current compared with that in a single AlON layer was achieved with these structures, while maintaining the superior thermal stability and electrical properties of the oxynitride/AlGaN interface. Consequently, distinct advantages in terms of the reliability of the gate dielectrics, such as an improved immunity against electron injection and an increased dielectric breakdown field, were demonstrated for AlGaN/GaN MOS capacitors with optimized stacked structures having a 3.3-nm-thick AlON interlayer.
- Published
- 2018
12. Implementation of atomic layer deposition-based AlON gate dielectrics in AlGaN/GaN MOS structure and its physical and electrical properties
- Author
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Takuji Hosoi, Satoshi Nakazawa, Heiji Watanabe, Takahiro Yamada, Mikito Nozaki, Takayoshi Shimura, Akitaka Yoshigoe, Yoshiharu Anda, Tetsuzo Ueda, Kenta Watanabe, and Hong-An Shih
- Subjects
Ozone ,Materials science ,Physics and Astronomy (miscellaneous) ,General Physics and Astronomy ,Synchrotron radiation ,chemistry.chemical_element ,Insulator (electricity) ,02 engineering and technology ,Dielectric ,01 natural sciences ,law.invention ,Atomic layer deposition ,chemistry.chemical_compound ,X-ray photoelectron spectroscopy ,law ,0103 physical sciences ,010302 applied physics ,business.industry ,General Engineering ,021001 nanoscience & nanotechnology ,Nitrogen ,Capacitor ,chemistry ,Optoelectronics ,0210 nano-technology ,business - Abstract
Alumina incorporating nitrogen (aluminum oxynitride; AlON) for immunity against charge injection was grown on a AlGaN/GaN substrate through the repeated atomic layer deposition (ALD) of AlN layers and in situ oxidation in ozone (O3) ambient under optimized conditions. The nitrogen distribution was uniform in the depth direction, the composition was controllable over a wide range (0.5–32%), and the thickness could be precisely controlled. Physical analysis based on synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS) revealed that harmful intermixing at the insulator/AlGaN interface causing Ga out-diffusion in the gate stack was effectively suppressed by this method. AlON/AlGaN/GaN MOS capacitors were fabricated, and they had excellent electrical properties and immunity against electrical stressing as a result of the improved interface stability.
- Published
- 2018
13. Improved hysteresis in a normally-off AlGaN/GaN MOS heterojunction field-effect transistor with a recessed gate structure formed by selective regrowth
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Satoshi Nakazawa, Masahiro Ishida, Naohiro Tsurumi, Tetsuzo Ueda, Yoshiharu Anda, Noboru Negoro, and Nanako Shiozaki
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Materials science ,Fabrication ,Physics and Astronomy (miscellaneous) ,General Physics and Astronomy ,Hardware_PERFORMANCEANDRELIABILITY ,02 engineering and technology ,01 natural sciences ,law.invention ,law ,0103 physical sciences ,Hardware_INTEGRATEDCIRCUITS ,Metal gate ,010302 applied physics ,business.industry ,Transistor ,General Engineering ,Heterojunction ,021001 nanoscience & nanotechnology ,Threshold voltage ,Hysteresis ,Optoelectronics ,Degradation (geology) ,Dry etching ,0210 nano-technology ,business ,Hardware_LOGICDESIGN - Abstract
A normally-off AlGaN/GaN MOS heterojunction field-effect transistor (MOS-HFET) with a recessed gate structure formed by selective area regrowth is demonstrated. The fabricated MOS-HFET exhibits a threshold voltage of 1.7 V with an improved hysteresis of 0.5 V as compared with a device fabricated by a conventional dry etching process. An analysis of capacitance–voltage (C–V) characteristics reveals that the dry etching process increases interface state density and introduces an additional discrete trap. The use of the selective area regrowth technique effectively suppresses such degradation, avoiding the MOS interface from being exposed to dry etching. The results presented in this paper indicate that the selective area regrowth technique is promising for the fabrication of normally-off AlGaN/GaN MOS-HFETs.
- Published
- 2017
14. Design and control of interface reaction between Al-based dielectrics and AlGaN layer in AlGaN/GaN metal-oxide-semiconductor structures
- Author
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Kenta Watanabe, Takuji Hosoi, Akitaka Yoshigoe, Takayoshi Shimura, Tetsuzo Ueda, Satoshi Nakazawa, Masahiro Ishida, Takahiro Yamada, Heiji Watanabe, Yoshiharu Anda, and Mikito Nozaki
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010302 applied physics ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Wide-bandgap semiconductor ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,Metal ,visual_art ,0103 physical sciences ,visual_art.visual_art_medium ,Optoelectronics ,Process window ,Thermal stability ,Diffusion (business) ,0210 nano-technology ,business ,Layer (electronics) ,Deposition (law) - Abstract
Important clues for achieving well-behaved AlGaN/GaN metal-oxide-semiconductor (MOS) devices with Al-based gate dielectrics were systematically investigated on the basis of electrical and physical characterizations. We found that low-temperature deposition of alumina insulators on AlGaN surfaces is crucial to improve the interface quality, thermal stability, and variability of MOS devices by suppressing Ga diffusion into the gate oxides. Moreover, aluminum oxynitride grown in a reactive nitric atmosphere was proven to expand the optimal process window that would improve the interface quality and to enhance immunity against charge injection into the gate dielectrics. The results constitute common guidelines for achieving high-performance and reliable AlGaN/GaN MOS devices.
- Published
- 2017
15. Comprehensive study on initial thermal oxidation of GaN(0001) surface and subsequent oxide growth in dry oxygen ambient
- Author
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Masahiro Ishida, Akitaka Yoshigoe, Takayoshi Shimura, Kenta Watanabe, Yoshiharu Anda, Joyo Ito, Mikito Nozaki, Heiji Watanabe, Takahiro Yamada, Ryohei Asahara, Tetsuzo Ueda, Takuji Hosoi, and Satoshi Nakazawa
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010302 applied physics ,Thermal oxidation ,Materials science ,Oxide ,General Physics and Astronomy ,Gallium nitride ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,Grain growth ,chemistry.chemical_compound ,Crystallography ,Chemical engineering ,X-ray photoelectron spectroscopy ,chemistry ,0103 physical sciences ,Crystallite ,0210 nano-technology - Abstract
Initial oxidation of gallium nitride (GaN) (0001) epilayers and subsequent growth of thermal oxides in dry oxygen ambient were investigated by means of x-ray photoelectron spectroscopy, spectroscopic ellipsometry, atomic force microscopy, and x-ray diffraction measurements. It was found that initial oxide formation tends to saturate at temperatures below 800 °C, whereas the selective growth of small oxide grains proceeds at dislocations in the epilayers, followed by noticeable grain growth, leading to a rough surface morphology at higher oxidation temperatures. This indicates that oxide growth and its morphology are crucially dependent on the defect density in the GaN epilayers. Structural characterizations also reveal that polycrystalline α- and β-phase Ga2O3 grains in an epitaxial relation with the GaN substrate are formed from the initial stage of the oxide growth. We propose a comprehensive model for GaN oxidation mediated by nitrogen removal and mass transport and discuss the model on the basis of ex...
- Published
- 2017
16. Super self-aligned GaAs RF switch IC with 0.25 dB extremely low insertion loss for mobile communication systems
- Author
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S. Makioka, K. Miyatsuji, Yoshiharu Anda, and Daisuke Ueda
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Source area ,Materials science ,business.industry ,Cellular radio ,Electrical engineering ,Capacitance ,Electronic, Optical and Magnetic Materials ,Gallium arsenide ,Power (physics) ,chemistry.chemical_compound ,RF switch ,chemistry ,Insertion loss ,Electrical and Electronic Engineering ,Mobile communication systems ,business - Abstract
An extremely low loss switch IC has been implemented by using a 0.15 /spl mu/m-gate super self-aligned FET with reduced drain/source area. Both off-state-capacitance and the specific on-resistance of the implemented FET have been dramatically reduced by the novel device structure. The experimentally fabricated switch IC showed the low insertion loss of 0.25 dB at an added power of 35 dBm at a frequency of 0.9 GHz, which is the lowest value ever reported.
- Published
- 2001
17. GaN Gate Injection Transistor with integrated Si Schottky barrier diode for highly efficient DC-DC converters
- Author
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Shinji Ujita, Yusuke Kinoshita, Satoshi Tamura, Yoshiharu Anda, Hidekazu Umeda, Tatsuo Morita, Tsuyoshi Tanaka, and Tetsuzo Ueda
- Subjects
Materials science ,Silicon ,business.industry ,Transistor ,Wide-bandgap semiconductor ,Schottky diode ,chemistry.chemical_element ,Converters ,Epitaxy ,law.invention ,chemistry ,law ,Optoelectronics ,business ,Low voltage ,Diode - Abstract
In this paper, we present a novel GaN-based normally-off transistor with an integrated Si Schottky barrier diode (SBD) for low voltage DC-DC converters. The integrated SBD is formed by the Si substrate for the epitaxial growth of AlGaN/GaN hetero-structure, which is connected to the normally-off GaN Gate Injection Transistor (GIT) over it with via-holes. The diode can flow the reverse current in the conversion operation with lower forward voltage than that of the lateral GaN transistor enabling lower operating loss. A DC-DC converter from 12V down to 1.3V using the integrated devices with the reduced gate length down to 0.5μm exhibits a high peak efficiency of 89% at 2MHz demonstrating the promising potential of GaN devices for the application.
- Published
- 2012
18. (Invited) Gate Stack Technology for Advanced AlGaN/GaN Mos-Hemt Power Devices
- Author
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Heiji Watanabe, Ryohei Asahara, Joyo Ito, Kenta Watanabe, Mikito Nozaki, Takahiro Yamada, Satoshi Nakazawa, Yoshiharu Anda, Masahiro Ishida, Tetsuzo Ueda, Akitaka Yoshigoe, Takuji Hosoi, and Takayoshi Shimura
- Abstract
AlGaN/GaN high electron mobility transistor (HEMT) has gained much attention as next-generation high frequency and high power devices. Since AlGaN/GaN HEMT with Schottky gate is restricted in device application due to large gate leakage current and normally-on operation, metal-oxide-semiconductor (MOS) gate stack with deposited gate insulator has been widely investigated to overcome these limitations. Among various insulating materials, aluminum based oxide such as Al2O3 is one of the potential candidate because of its wide bandgap and high thermal stability. However, large amount of interface traps at MOS interfaces severely degrade both carrier mobility and threshold voltage (Vth) stability. Furthermore, significant electron injection into Al2O3 layer causing positive Vth shift was often observed for Al2O3/AlGaN/GaN MOS-HEMT. We have recently reported that N incorporation into Al2O3 (aluminum oxynitride) significantly reduces not only the negative fixed charges but also the electron traps in Si and SiC MOS devices. In this study, superior physical and electrical properties of AlON gate dielectrics on AlGaN/GaN substrates were demonstrated. We fabricated high-quality AlON/AlGaN/GaN MOS capacitors with improved stability against charge injection and a reduced interface state density. Moreover, the impact of nitrogen incorporation into the gate insulator will be discussed on the basis of results from physical characterizations.
- Published
- 2016
19. GaN-based multi-junction diode with low reverse leakage current using P-type barrier controlling layer
- Author
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Yoshiharu Anda, Kazuhiro Kaibara, Daisuke Ueda, Tsuyoshi Tanaka, Yasuhiro Yamada, Hidetoshi Ishida, Tatsuo Morita, Daisuke Shibata, Tomohiro Murata, Tetsuzo Ueda, and Masahiro Ishida
- Subjects
Materials science ,Avalanche diode ,business.industry ,Schottky diode ,Backward diode ,Cathode ,Anode ,law.invention ,Reverse leakage current ,law ,Optoelectronics ,business ,Step recovery diode ,Diode - Abstract
We present a novel GaN-based diode with low reverse leakage current which ensures the high voltage operation up to 600V. The diode consists of multi-junctions of AlGaN/GaN with a p-GaN overlayer where the anode and cathode are formed on the sidewalls of the channels. The tunneling current which is the origin of the leakage current can be reduced by controlling the potential barrier at the anode sidewall by means of the depletion layer from the p-GaN. The fabricated GaN diode with the p-type barrier controlling layer (BCL) exhibits high forward current of 18A at 1.5V with the breakdown voltages over 600V taking advantages of the reduced leakage current. The fabricated GaN-based diode has smaller R on C of 70 pΩF than 95 pΩF of the commercially available SiC Schottky barrier diode (SBD) indicating that the GaN diode is suitable for power switching. The GaN diode exhibits high conversion efficiency of 98.2 % in the voltage boosting converter at the output voltage of 400V by combining it with a GaN Gate Injection Transistor (GIT). The obtained performance by using the GaN diode is superior to that with a SiC SBD.
- Published
- 2011
20. High-Power and High-Gain S-band AlGaN/GaN HFETs with Source Field Plates on Si Substrate
- Author
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Masaaki Nishijima, Naohiro Tsurumi, Satoshi Nakazawa, Tsuneo Tanaka, Masahiro Ishida, T. Ueda, and Yoshiharu Anda
- Subjects
High-gain antenna ,Materials science ,Si substrate ,business.industry ,Optoelectronics ,Algan gan ,S band ,business ,Source field ,Power (physics) - Published
- 2011
21. 99.3% Efficiency of three-phase inverter for motor drive using GaN-based Gate Injection Transistors
- Author
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Tetsuzo Ueda, Daisuke Ueda, Satoshi Tamura, Masahiro Ishida, Tatsuo Morita, Yasuhiro Uemoto, Yoshiharu Anda, and Tsuyoshi Tanaka
- Subjects
Engineering ,business.industry ,Transistor ,Electrical engineering ,Gallium nitride ,Hardware_PERFORMANCEANDRELIABILITY ,Insulated-gate bipolar transistor ,law.invention ,Threshold voltage ,chemistry.chemical_compound ,Current injection technique ,chemistry ,law ,Logic gate ,Hardware_INTEGRATEDCIRCUITS ,Inverter ,business ,Hardware_LOGICDESIGN ,Diode - Abstract
In this paper, we present a successful operation of Gallium Nitride(GaN)-based three-phase inverter with high efficiency of 99.3% for driving motor at 900W under the carrier frequency of 6kHz. This efficiency well exceeds the value by IGBT (Insulated Gate Bipolar Transistor). This demonstrates that GaN has a great potential for power switching application competing with SiC. Fully reduced on-state resistance in a new normally-off GaN transistor called Gate Injection Transistor (GIT) greatly helps to increase the efficiency. In addition, use of the bidirectional operation of the lateral and compact GITs with synchronous gate driving, the inverter is operated free from fly-wheel diodes which have been connected in parallel with IGBTs in a conventional inverter system.
- Published
- 2011
22. Blocking-voltage boosting technology for GaN transistors by widening depletion layer in Si substrates
- Author
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Asamira Suzuki, Hidekazu Umeda, Tsuyoshi Tanaka, Masahiro Ishida, Yoshiharu Anda, Daisuke Ueda, and Tetsuzo Ueda
- Subjects
Materials science ,business.industry ,Transistor ,Channel-stopper ,Wide-bandgap semiconductor ,Gallium nitride ,law.invention ,chemistry.chemical_compound ,Ion implantation ,Depletion region ,chemistry ,law ,Breakdown voltage ,Optoelectronics ,Field-effect transistor ,business - Abstract
We propose a novel technique to boost the blocking voltage of AlGaN/GaN hetero junction field effect transistors (HFETs) by widening a depletion layer in highly resistive Si substrate. The blocking-voltage boosting (BVB) technology utilizes ion implantation at the peripheral area of the chip as channel stoppers to terminate the leakage current from the interfacial inversion layers at AlN/Si. A depletion layer is widened in the substrate by the help of the channel stopper, which increases the blocking voltage of the HFET. The off-state breakdown voltage of the HFETs is increased up to 1340V by the BVB technology from 760V without the channel stoppers for the epitaxial GaN as thin as 1.4µm on Si. This technology greatly helps to increase the blocking voltage even for thin epitaxial GaN on Si, which leads to further reduction of the fabrication cost.
- Published
- 2010
23. Recent Advances in GaN Power Switching Devices
- Author
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Yoshiharu Anda, Daisuke Ueda, Tsuyoshi Tanaka, Yasuhiro Uemoto, Satoshi Tamura, Masahiro Ishida, and Tetsuzo Ueda
- Subjects
Materials science ,business.industry ,Transistor ,Electrical engineering ,Gallium nitride ,Hardware_PERFORMANCEANDRELIABILITY ,Insulated-gate bipolar transistor ,Integrated circuit ,law.invention ,chemistry.chemical_compound ,Ion implantation ,chemistry ,law ,Logic gate ,Hardware_INTEGRATEDCIRCUITS ,Optoelectronics ,Inverter ,Wafer ,business - Abstract
Recent advances in GaN power switching devices are reviewed. A new normall-off GaN transistor called Gate Injection Transistor (GIT) increases drain current by conductivity modulation. The GIT is fabricated on cost-effective Si substrates by novel MOCVD technology enabling crack-free and smooth surfaces over 6-inch wafer. These technologies with thermally stable device isolation by Fe ion implantation are applied for a monolithic inverter IC. This is the world fist demonstration of a GaN inverter IC for motor drive, which reduces the total operating loss by 42% from that by the IGBT-based inverter. These technologies are indispensable for wide-spread use of GaN power switching transistors in the future.
- Published
- 2010
24. Thermally Stable Isolation of AlGaN/GaN Transistors by Using Fe Ion Implantation
- Author
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Tetsuzo Ueda, Tsuyoshi Tanaka, Hidekazu Umeda, Yoshiharu Anda, and Toshiyuki Takizawa
- Subjects
Ion implantation ,Materials science ,Isolation (health care) ,law ,business.industry ,Transistor ,Optoelectronics ,Algan gan ,business ,law.invention - Published
- 2010
25. High-efficiency thin and compact concentrator photovoltaics using micro-solar cells with via-holes sandwiched between thin lens-array and circuit board
- Author
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Akihiro Itou, Eiji Fujii, Masaki Yamamoto, Onur Fidaner, Hidekazu Arase, Tohru Nakagawa, Daisuke Ueda, Tetsuzo Ueda, Inoue Kazuo, Hidetoshi Ishida, Yoshiharu Anda, Nobuhiko Hayashi, Tetsuya Asano, Ryutaro Futakuchi, Akio Matsushita, Michael W. Wiemer, and Daijiro Inoue
- Subjects
Materials science ,integumentary system ,business.industry ,Photovoltaic system ,Energy conversion efficiency ,General Engineering ,food and beverages ,General Physics and Astronomy ,Nanotechnology ,law.invention ,Printed circuit board ,Optics ,law ,Thin lens ,biological sciences ,Solar cell ,Electrode ,Optoelectronics ,Concentrated photovoltaics ,Air gap (plumbing) ,business - Abstract
We have developed a compact concentrator photovoltaic (CPV) module that comprises micro-solar cells with an area of ≈0.6 × 0.6 mm2 sandwiched between a 20-mm-thick lens array and a 1-mm-thick circuit board with no air gap. To establish electrical connections between the circuit board and the micro-solar cells, we developed a micro-solar cell with positive and negative electrodes on the lower face of the cell. In this study, we demonstrated the photovoltaic performance of the micro-solar cell closely approaches that of the standard solar cell measuring ≈5 × 5 mm2 commonly used in conventional CPVs under concentrated illumination. Our study showed that the negative effect on PV performance of perimeter carrier recombination in the micro-solar cell was insignificant under concentrated illumination. Finally, we assembled our micro-solar cells into a CPV module and achieved the module energy conversion efficiency of 34.7% under outdoor solar illumination.
- Published
- 2014
26. 200 W Output Power at S-Band in AlGaN/GaN Heterojunction Field Effect Transistors with Field Plates on Si Substrates
- Author
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Tetsuzo Ueda, Yoshiharu Anda, Naohiro Tsurumi, Satoshi Nakazawa, Masaaki Nishijima, Tsuyoshi Tanaka, and Masahiro Ishida
- Subjects
Materials science ,Fabrication ,Physics and Astronomy (miscellaneous) ,business.industry ,General Engineering ,General Physics and Astronomy ,Heterojunction ,Equivalent circuit ,Optoelectronics ,Output impedance ,Field-effect transistor ,S band ,business ,Microwave ,Voltage - Abstract
Use of Si substrates for the fabrication of microwave AlGaN/GaN heterojunction field effect transistors (HFETs) has been strongly desired for the low cost fabrication. The performance so far has never been satisfactory in view of the output power and the gain as compared with those on SiC substrates. In this paper, AlGaN/GaN HFETs on Si with high output power of 203 W and high linear gain of 16.9 dB at 2.5 GHz are demonstrated. The HFETs have field plates to reduce the feedback capacitance leading to higher gain, of which a new design of the field plates enables high power as well. The structural design is based on the equivalent circuit model using the device parameters extracted from the small signal RF performances. Here, it is found that shortening the field plate length down to 0.6 µm results in the high output power owing to the stable output impedance for various drain voltage. Note that the conditions of the epitaxial growth are optimized to achieve high current density of 850 mA/mm with both the high mobility and high sheet carrier concentration. The device processing is established so as to achieve the high power operation free from the current collapse. The device can be operated at the drain voltage as high as 50 V, which enables the 200 W output power. The presented AlGaN/GaN HFETs are very promising for various microwave applications including cellular base stations, which would lower the system cost taking advantage of cost-effective Si substrates.
- Published
- 2012
27. Quantum Analysis of Hole Distribution in Multiple-Delta-Doped Diamond with a Deep Impurity Level
- Author
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Yoshiharu Anda, Yoshiharu Anda, primary, Takuya Ariki, Takuya Ariki, additional, and Takeshi Kobayashi, Takeshi Kobayashi, additional
- Published
- 1995
- Full Text
- View/download PDF
28. Novel fabrication technique for 0.1 μm T-shaped gate with i-line negative resist and poly(methylmethacrylate)
- Author
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Manabu Yanagihara, Toshiaki Matsui, Katsunori Nishii, Tomoya Uda, Inoue Kaoru, Yoshiharu Anda, Mitsuru Tanabe, Toshinobu Matsuno, and Nobumitsu Hirose
- Subjects
Fabrication ,Materials science ,business.industry ,General Engineering ,Analytical chemistry ,High-electron-mobility transistor ,Photoresist ,Gallium arsenide ,chemistry.chemical_compound ,Resist ,chemistry ,Optoelectronics ,Dry etching ,business ,Lithography ,Electron-beam lithography - Abstract
We report on a novel fabrication technique for 0.1 μm T-shaped gates using electron beam and i-line lithography. This technique adopts a TLOR-N001 (i-line negative resist)/950k poly(methylmethacrylate) (PMMA) bilayer system. From Fourier-transform infrared spectrum analysis, we found a 70 nm mixed layer of PMMA and TLOR was formed at the interface of these resists which offers suitable overcut resist profile for the T-shaped gate but also enhances the resistance of the PMMA against dry etching. By utilizing this process, we obtained a 0.12 μm gate length T-shaped gate and applied it to the fabrication of an AlGaAs/InGaAs pseudomorphic high electron mobility transistor with a fT and fmax as high as 66 and 190 GHz.
- Published
- 1999
29. Hall Effect Measurement and Band Bending Calculation of Hydrogenated Diamond Film Grown by Chemical Vapor Deposition
- Author
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Yusuke Shirakawa, Tetsuro Maki, Yoshiharu Anda, and Takeshi Kobayashi
- Subjects
Condensed matter physics ,Chemistry ,Fermi level ,General Engineering ,General Physics and Astronomy ,Diamond ,Chemical vapor deposition ,engineering.material ,Semimetal ,symbols.namesake ,Surface conductivity ,Band bending ,Hall effect ,engineering ,symbols ,Thin film - Abstract
The surface conductive layer in a hydrogenated chemical vapor deposited diamond film was studied experimentally and analytically. The Hall effect measurement showed that the hole areal density at the surface introduced unintentionally was as high as 1013/ cm2, which was about an order of magnitude higher than that used in the conventional field-effect transistors. We have analyzed the surface band bending from the quantum-mechanical point of view to determine the equivalent Fermi level pinning position settled after hydrogenation. It was found that, at the surface, the Fermi level locates inside the valence band at a depth of 0.36 eV from the valence band edge.
- Published
- 1997
30. Effects of post-deposition annealing in O2 on threshold voltage of Al2O3/AlGaN/GaN MOS heterojunction field-effect transistors.
- Author
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Satoshi Nakazawa, Hong-An Shih, Naohiro Tsurumi, Yoshiharu Anda, Tsuguyasu Hatsuda, Tetsuzo Ueda, Tsunenobu Kimoto, and Tamotsu Hashizume
- Abstract
In this paper, we investigated the effects of the post-deposition annealing (PDA) on the threshold voltage (V
th ) of AlGaN/GaN MOS heterojunction field-effect transistors with atomic-layer-deposited Al2 O3 using H2 O vapor or oxygen plasma as the oxidant. By PDA, the Vth shifts positively with the Vth variations depending on the oxidants. The capacitance–voltage measurements reveal that the Vth variation is attributed to the differences in the initial fixed charge density in the Al2 O3 or/and the Al2 O3 /AlGaN for both oxidants. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
31. Implementation of atomic layer deposition-based AlON gate dielectrics in AlGaN/GaN MOS structure and its physical and electrical properties.
- Author
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Mikito Nozaki, Kenta Watanabe, Takahiro Yamada, Hong-An Shih, Satoshi Nakazawa, Yoshiharu Anda, Tetsuzo Ueda, Akitaka Yoshigoe, Takuji Hosoi, Takayoshi Shimura, and Heiji Watanabe
- Abstract
Alumina incorporating nitrogen (aluminum oxynitride; AlON) for immunity against charge injection was grown on a AlGaN/GaN substrate through the repeated atomic layer deposition (ALD) of AlN layers and in situ oxidation in ozone (O
3 ) ambient under optimized conditions. The nitrogen distribution was uniform in the depth direction, the composition was controllable over a wide range (0.5–32%), and the thickness could be precisely controlled. Physical analysis based on synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS) revealed that harmful intermixing at the insulator/AlGaN interface causing Ga out-diffusion in the gate stack was effectively suppressed by this method. AlON/AlGaN/GaN MOS capacitors were fabricated, and they had excellent electrical properties and immunity against electrical stressing as a result of the improved interface stability. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
32. SiO2/AlON stacked gate dielectrics for AlGaN/GaN MOS heterojunction field-effect transistors.
- Author
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Kenta Watanabe, Daiki Terashima, Mikito Nozaki, Takahiro Yamada, Satoshi Nakazawa, Masahiro Ishida, Yoshiharu Anda, Tetsuzo Ueda, Akitaka Yoshigoe, Takuji Hosoi, Takayoshi Shimura, and Heiji Watanabe
- Abstract
Stacked gate dielectrics consisting of wide bandgap SiO
2 insulators and thin aluminum oxynitride (AlON) interlayers were systematically investigated in order to improve the performance and reliability of AlGaN/GaN metal–oxide–semiconductor (MOS) devices. A significantly reduced gate leakage current compared with that in a single AlON layer was achieved with these structures, while maintaining the superior thermal stability and electrical properties of the oxynitride/AlGaN interface. Consequently, distinct advantages in terms of the reliability of the gate dielectrics, such as an improved immunity against electron injection and an increased dielectric breakdown field, were demonstrated for AlGaN/GaN MOS capacitors with optimized stacked structures having a 3.3-nm-thick AlON interlayer. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
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