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Nozaki, Mikito*; Terashima, Daiki*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; Watanabe, Heiji*
Japanese Journal of Applied Physics, 59(SM), p.SMMA07_1 - SMMA07_7, 2020/07
Times Cited Count：2 Percentile：12.12(Physics, Applied)AlGaN/GaN metal-oxide-semiconductor (MOS) structures were fabricated by low-power inductively coupled plasma reactive ion etching and chemical vapor deposition of SiO
dielectrics on the etched surfaces, and they were systematically investigated by physical and electrical characterizations in an effort to develop a low-damage recessed gate process. The comprehensive research demonstrates the significant advantages of the proposed low-damage recessed gate process for fabricating next-generation AlGaN/GaN MOS-HFET devices.
Abderrahmane, A.*; Takahashi, Hiroki*; Tashiro, Tatsuya*; Ko, P. J.*; Okada, Hiroshi*; Sato, Shinichiro; Oshima, Takeshi; Sandhu, A.*
AIP Conference Proceedings 1585, p.123 - 127, 2014/02
Times Cited Count：1 Percentile：50.91(Physics, Applied)The effect of annealing at 673 K on irradiated micro-Hall sensors irradiated with protons at 380 keV and fluences of 1
cm
, 1
cm, 1
cm is reported. Cathodoluminescence measurements were carried out at room temperature before and after annealing and showed improvement in the band edge band emission of the GaN layer. After annealing a sensor irradiated by 1 cm the device became operational with improvements in its magnetic sensitivity. All irradiated sensors showed improvement in their electrical characteristics after annealing.
Abderrahmane, A.*; Tashiro, Tatsuya*; Takahashi, Hiroki*; Ko, P. J.*; Okada, Hiroshi*; Sato, Shinichiro; Oshima, Takeshi; Sandhu, A.*
Applied Physics Letters, 104(2), p.023508_1 - 023508_4, 2014/01
Times Cited Count：6 Percentile：26.7(Physics, Applied)The effect of annealing on the magnetoelectrical properties of proton-irradiated micro-Hall sensors at an energy of 380 keV and very high proton fluences was studied. Recovery of the electron mobility and a decrease in the sheet resistance of the annealed micro-Hall sensors, as well as an enhancement in their magnetic sensitivity were reported. Trap removal and an improvement in the crystal quality by removing defects were confirmed through current-voltage measurements and Raman spectroscopy, respectively.
Abderrahmane, A.*; Koide, Shota*; Okada, Hiroshi*; Takahashi, Hiroki*; Sato, Shinichiro; Oshima, Takeshi; Sandhu, A.*
Applied Physics Letters, 102(19), p.193510_1 - 193510_4, 2013/05
Times Cited Count：10 Percentile：41.04(Physics, Applied)The magnetoelectric properties of AlGaN/GaN micro-Hall effect sensors were studied after 380 keV proton irradiation. After irradiation the current-voltage measurements, stability of the magnetic sensitivity of the sensors, and the sheet electron density were degraded with a dramatic decrease of the electron mobility at high temperatures. Raman spectroscopy showed a degradation in the crystalline quality of GaN crystal, but there was no change in the strain.
Ga
N and InN crystals under high pressuresSaito, Hiroyuki; Utsumi, Wataru; Kaneko, Hiroshi*; Aoki, Katsutoshi
Proceedings of Joint 20th AIRAPT - 43rd EHPRG International Conference on High Pressure Science and Technology (CD-ROM), 4 Pages, 2005/06
We have performed synthesis studies of various III-V nitrides crystals, key materials for optoelectronic and high-power/frequency devices, using a cubic-anvil-type large volume high-pressure apparatus combined with in situ X-ray diffraction. Polly-crystallines of AlGaN alloys covering a composition range of 0 
x 1 were synthesized by a solid-phase reaction under high pressure. In situ X-ray diffraction profiles were measured to observe the alloying process, which started at around 800
C under 6.0 GPa. Single crystal of Al
Ga
N was also successfully obtained by slow cooling of its melt from 2400C at 6.5 GPa. For InN, its phase diagram was determined under high P-T conditions up to 20GPa and 2000C based on the in situ observations, which demonstrates that 19GPa and 1900C are needed for its congruent melting.
Saito, Hiroyuki; Utsumi, Wataru; Kaneko, Hiroshi*; Kiriyama, Koji*; Aoki, Katsutoshi
State-of-the-Art Program on Compound Semiconductors XLI and Nitride and Wide Bandgap Semiconductors for Sensors, Photonics, and Electronics V, p.587 - 592, 2004/10
Single crystals of GaN were successfully synthesized by slowly cooling its stoichiometric melt under high pressure. Applying high pressures above 6.0 GPa prevented decomposition and allowed the congruent melt of GaN at 2220C, which was confirmed by an in situ X-ray diffraction study. Using a cubic-anvil-type, large volume, high-pressure apparatus and a GaN powder as a starting material, single crystal growth was achieved by reducing the temperature from 2400C at 6.5 GPa. The X-ray rocking curve of the recovered sample showed a very narrow line width, less than 30 arcsec, suggesting a low dislocation density. Bulk specimens of Al
GaN alloys, which covered a composition range of 0x1 were also synthesized under high pressures.
GaN alloy by solid-phase reaction under high pressureSaito, Hiroyuki; Utsumi, Wataru; Kaneko, Hiroshi*; Aoki, Katsutoshi
Japanese Journal of Applied Physics, Part 2, 43(7B), p.L981 - L983, 2004/07
Times Cited Count：5 Percentile：23.95(Physics, Applied)Bulk specimens of AlGaN alloys covering a composition range of 0
1 were synthesized by a solid-phase reaction under high pressure. 
X-ray diffraction profiles were measured to observe the alloying process, which began at around 800C under 6.0 GPa. SEM observation and X-ray analysis of the recovered specimen indicated a uniform distribution of Al and Ga and continuous variations of the lattice constants against the composition, which implies that a solid solution of AlN and GaN is formed regardless of atomic composition.
GaN(0
x1)Nakanishi, Yasuo*; Wakahara, Akihiro*; Okada, Hiroshi*; Yoshida, Akira*; Oshima, Takeshi; Ito, Hisayoshi; Shibata, Tomohiko*; Tanaka, Mitsuhiro*
Physica Status Solidi, 0(7), p.2623 - 2626, 2003/07
In our previous study, it was reported that Eu-doped Nitride semiconductors show luminescence propetires. In this study, we investigate the relationship between luminescence properties and Al composition using AlGaN(0x1). AlGaN were grown using OMVPE. Eu atoms were doped into the samples by ion implantation (200keV). After implantation, the samples were annealed to remove residual damege. Luminescence propreties of the samples were measured using photoluminescence and cathodeluminescence. As a result, luminescence at 621 nm which relates 4f-4f transition were observed for all samples (x=0 to 1). As for intensity, samples with x=0.5 show the strongest luminescence. This result can be interpreted in terms of the internal stress of crystals by the existence of Al atoms.
