Papers by Keyword: AlGaN

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Authors: Seikoh Yoshida, Mitsuru Masuda, Yuki Niiyama, Jiang Li, Nariaki Ikeda, Takehiko Nomura
Abstract: We report on the 288 V-10 V DC- DC converter circuit using AlGaN/GaN HFETs for the first time. The AlGaN/GaN HFET with a large current and a high breakdown voltage operation was fabricated. That is, the maximum drain current was over 50 A, and the minimum on-resistance was 70 mohm. The breakdown voltage was over 600 V. A DC-DC down-converter from input DC 288 V to output DC 10 V was fabricated using these HFETs. It was confirmed that the switching speed of the AlGaN/GaN HFET was faster than that of Si MOSFET. The DC-DC down-converter was fabricated using these HFETs. This converter was composed of a full bridge circuit using four n-channel AlGaN/GaN HFETs. In the case of AlGaN/GaN HFET, a gate switching wave (Vgs) and source-drain wave (Vds) were abrupt compared with those of using Si MOSFETs. In both cases, a stable and constant output DC 10V was also obtained and the conversion efficiency of the converters with AlGaN/GaN HFETs was 84%.
Authors: A.Y. Hudeish, C.K. Tan, Azlan Abdul Aziz, Hassan Zainuriah
Abstract: There is a particular interest in the development of wide band gap semiconductor gas sensor because of their potential for high temperature operation and the ability to integrate them with power or microwave electrodes or with UV solar-blind detector and emitters fabricated in the same materials. AlGaN based devices are attractive for gas sensing in automotive exhausts and flow-gas, because of strong spontaneous polarization of AlGaN (free carrier concentration profiles inside this material that is very sensitive to any manipulation of surface change). In this report, we characterized the Ni/AlGaN/Sapphire Schottky barriers as hydrogen gas sensor at temperature range of 25°C to 500°C. A change in forward current was obtained in response to a change in ambient from pure N2 to 2% H2/ 98% N2, higher than the change in forward current obtained in Ni/GaN or Ni/Si Schottky diodes measured under the same conditions. The sensor response time was independent on the rate of mass transport of gas into the test chamber, while at high temperature, dissociation of gas controlled by the diffusion of atomic hydrogen through the metal/AlGaN surface, increased the sensor response time.
Authors: Tong Ho Kim, Soo Jeong Choi, April S. Brown, Maria Losurdo, Giuseppe Valerio Bianco, Maria M. Giangregorio, Giovanni Bruno
Abstract: Nitride materials are critical for a range of applications, including UV-visible light emitting diodes (LEDs). Advancing the performance, reliability and synthesis of AlGaN/GaN and InGaN/GaN heterojunction devices requires a systematic methodology enabling characterization of key metric like alloy composition, thickness and quality possibly in real time. This contribution reports on the real time characterization of the plasma assisted molecular beam epitaxy of AlGaN/GaN and InGaN/GaN heterostructures. Spectroscopic ellipsometry real time monitoring has revealed a number of key process and material iusses, such as the roughening of the GaN templates depending on plasma exposure during the substrate cleaning step, the composition of the alloy and the growth mode. Parameters like the plasma conditions, the surface temperature and the atomic flow ratio are investigated to understand the interplay process-material composition-structure-optical properties.
Authors: Katja Tonisch, Robert Benzig, Gernot Ecke, Jörg Pezoldt
Abstract: The growth of AlGaN solid solutions on 3C-SiC(111)/Si(111) is demonstrated. The residual stress of the grown layer was investigated by high resolution X-ray diffraction (HRXRD) and infrared ellipsometry. Analysis of the HRXRD data showed that the observed lattice distortion was caused partially by hydrostatic pressure and partially by biaxial tension. The residual stress depends on the layer composition and weakly on the growth temperature.
Authors: Seikoh Yoshida, Hirotatsu Ishii, Jiang Li
Authors: Hiroshi Amano, Masataka Imura, Motoaki Iwaya, Satoshi Kamiyama, Isamu Akasaki
Abstract: The fundamental growth issues of AlN and AlGaN on sapphire and SiC using metalorganic vapor phase epitaxy, particularly the growth of AlN and AlGaN on a groove-patterned template are reviewed. In addition, the conductivity control of AlGaN is shown. The conductivity control of p-type AlGaN, particularly the realization of a high hole concentration, is essential for realizing high-efficiency UV and DUV LEDs and LDs.
Authors: Yun Bai, Hua Jun Shen, Cheng Zhan Li, Yi Dan Tang, Xin Yu Liu
Abstract: The n-p-i-n AlGaN solar-blind ultraviolet double heterojunction phototransistor (DHPT) with internal gain is proposed and optimized in this paper. The dependences of spectral responsivity and quantum gain on structure parameters of the AlGaN DHPT are simulated in detail. Then, the polarization effect of AlGaN heterojunction on the performance of AlGaN DHPT is also investigated. Results show that positive polarization charge would enhance the photoresponse of the device, whereas the negative polarization charge would reduce the photoresponse significantly. The reasons for the polarization effect on performance of AlGaN DHPT are discussed.
Authors: Hui Liao, Wei Hua Chen, Fen Fen Wei, Juan Hou
Abstract: AlGaN/GaN superlattice are the important structure of optoelectronic devices such as light-emitting diodes and laser diodes. The nanostructure of the superlattice can greatly influences the optical electrical properties of final LD and LED . It is impossible to evaluate their thickness by TEM when it’s aluminum component lower than 14%.We investigated the nanostructure of strained p-type Al0.11Ga0.89N/GaN superlattice grown on sapphire by high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).By an average filtering technique, the thickness of the AlGaN layers and GaN layers were determined to be 2.409±0.092 nm and 2.371±0.062 nm from the HAADF-STEM images, respectively.
Authors: Kenneth A. Jones, T.S. Zheleva, R.D. Vispute, Shiva S. Hullavarad, M. Ervin, S. Dhar
Abstract: At sufficiently high temperatures PLD deposited TaC films can be grown epitaxially on 4H-SiC (0001) substrates; at lower temperatures the films recrystallize and ball up forming a large number of pinholes. The growth temperature for epitaxy was found to be 1000°C, and it was facilitated by the epitaxial growth of a thin (2 nm) transition layer of hexagonal Ta2C. High temperature annealing produced changes in the surface morphology, caused grain growth, and created pin holes through a recrystallization process in the films deposited at the lower temperatures, while the films deposited at the higher temperatures remained virtually unchanged. Using TEM it is shown that the (0001) basal planes of the hexagonal 4H-SiC and Ta2C phases are aligned, and they were also parallel to the (111) plane in the cubic TaC with the [101] cubic direction being parallel to the hexagonal [2110] hexagonal direction. The Ta2C interlayer most likely is formed because its lattice parameter in the basel plane (3.103 Ǻ) is intermediate between that of the 4H-SiC (3.08 Ǻ) and the TaC (3.150 Ǻ). Given that Al.5Ga.5N is lattice matched to TaC, it could be an excellent substrate for the growth of GaN/AlGaN heterostructures.
Authors: Nobuaki Teraguchi, Akira Suzuki, Y. Nanishi
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