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167 results on '"Shigekawa, N."'

5. Improved electrical properties of n-n and p-n Si/SiC junctions with thermal annealing treatment.

Author

Liang, J., Nishida, S., Arai, M., and Shigekawa, N.

Subjects
ANNEALING of metals, ELECTRIC potential, CAPACITANCE-voltage characteristics, TEMPERATURE, FERMI level, THERMIONIC emission
Abstract

The effects of annealing process on the electrical properties of n+-Si/n-SiC and p+-Si/n-SiC junctions fabricated by using surface-activated bonding are investigated. It is found by measuring the current-voltage (I-V) characteristics of n+-Si/n-SiC junctions that the reverse-bias current and the ideality factor decreased to 2.0×10-5mA/cm² and 1.10, respectively, after the junctions annealing at 700 °C. The flat band voltages of n+-Si/n-SiC and p+-Si/n-SiC junctions obtained from capacitance-voltage (C-V) measurements decreased with increasing annealing temperature. Furthermore, their flat band voltages are very close to each other irrespective of the annealing temperature change, which suggests that the Fermi level is still pinned at the bonding interface even for the junctions annealing at high temperature and the interface state density causing Fermi level pinning varies with the junctions annealing. The reverse characteristics of n+ -Si/n-SiC junctions are in good agreement with the calculations based on thermionic field emission. In addition, the calculated donor concentration of 4H-SiC epi-layers and flat band voltage is consistent with the values obtained from C-V measurements. [ABSTRACT FROM AUTHOR]

Published
2016
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8. Electrical properties of Si/Si interfaces by using surface-activated bonding.

Author

Liang, J., Miyazaki, T., Morimoto, M., Nishida, S., and Shigekawa, N.

Subjects
ELECTRIC properties of silicon, TRANSMISSION electron microscopy, ENERGY dispersive X-ray spectroscopy, POOLE-Frenkel effect, HIGH field effects (Electric fields)
Abstract

Electrical properties of n-Si/n-Si, p-Si/n-Si, and p--Si/n+-Si junctions fabricated by using surface-activated-bonding are investigated. The transmission electron microscopy/energy dispersive X-ray spectroscopy of the n-Si/n-Si interfaces reveals no evidence of oxide layers at the interfaces. From the current-voltage (I-V) and the capacitance-voltage (C-V) characteristics of the p-Si/n-Si and p--Si/n+-Si junctions, it is found that the interface states, likely to have formed due to the surface activation process using Ar plasma, have a more marked impact on the electrical properties of the p-Si/n-Si junctions. An analysis of the temperature dependence of the I-V characteristics indicates that the properties of carrier transport across the bonding interfaces for reverse-bias voltages in the p-Si/n-Si and p--Si/n+-Si junctions can be explained using the trap-assisted-tunneling and Frenkel-Poole models, respectively. [ABSTRACT FROM AUTHOR]

Published
2013
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12. Measurement of valence-band offsets of InAlN/GaN heterostructures grown by metal-organic vapor phase epitaxy.

Author

Akazawa, M., Gao, B., Hashizume, T., Hiroki, M., Yamahata, S., and Shigekawa, N.

Subjects
HETEROSTRUCTURES, EPITAXY, METAL organic chemical vapor deposition, X-ray photoelectron spectroscopy, CONDUCTION bands
Abstract

The valence band offsets, ΔEV, of In0.17Al0.83N/GaN, In0.25Al0.75N/GaN, and In0.30Al0.70N/GaN heterostructures grown by metal-organic vapor phase epitaxy were evaluated by using x-ray photoelectron spectroscopy (XPS). The dependence of the energy position and the full width at half maximum of the Al 2p spectrum on the exit angle indicated that there was sharp band bending caused by the polarization-induced electric field combined with surface Fermi-level pinning in each ultrathin InAlN layer. The ΔEV values evaluated without taking into account band bending indicated large discrepancies from the theoretical estimates for all samples. Erroneous results due to band bending were corrected by applying numerical calculations, which led to acceptable results. The evaluated ΔEV values were 0.2±0.2 eV for In0.17Al0.83N/GaN, 0.1±0.2 eV for In0.25Al0.75N/GaN, and 0.0±0.2 eV for In0.30Al0.70N/GaN. Despite the large decrease of around 1.0 eV in the band gap of InAlN layers according to the increase in the In molar fraction, the decrease in ΔEV was as small as 0.2 eV. Therefore, the change in band-gap discontinuity was mainly distributed to that in conduction band offset. [ABSTRACT FROM AUTHOR]

Published
2011
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42. Al0.44Ga0.56N spacer layer to prevent electron accumulation inside barriers in lattice-matched InAlN/AlGaN/AlN/GaN heterostructures

Author

Akazawa, M., Gao, B., Hashizume, T., Hiroki, M., Yamahata, S., Shigekawa, N., Akazawa, M., Gao, B., Hashizume, T., Hiroki, M., Yamahata, S., and Shigekawa, N.

Abstract

The barrier structure in lattice-matched InAlN/GaN heterostructures with AlGaN-based spacer layers grown by metal organic vapor phase epitaxy was studied by the capacitance-voltage (C-V) method. To investigate the characteristics under positive bias, an Al2O3 overlayer was added. The C-V characteristic of a sample with an Al0.38Ga0.62N (5 nm)/AlN (0.75 nm) double spacer layer exhibited an anomalous saturation at a value far below the insulator capacitance under positive bias, which indicated electron accumulation at the InAlN/AlGaN interface. The C-V characteristic of an alternative sample with a single Al0.44Ga0.56N (1.5 nm) spacer layer did not exhibit the anomalous saturation.

Published
2011

43. Small valence-band offset of In0.17Al0.83N/GaN heterostructure grown by metal-organic vapor phase epitaxy

Author

Akazawa, M., Matsuyama, T., Hashizume, T., Hiroki, M., Yamahata, S., Shigekawa, N., Akazawa, M., Matsuyama, T., Hashizume, T., Hiroki, M., Yamahata, S., and Shigekawa, N.

Abstract

The valence-band offset of a lattice-matched In0.17Al0.83N/GaN heterostructure grown by metal-organic vapor phase epitaxy (MOVPE) was investigated by x-ray photoelectron spectroscopy (XPS). Atomic force microscopy and angle-resolved XPS indicated that a thin In0.17Al0.83N (2.5 nm) layer was successfully grown by MOVPE on GaN. The XPS result showed that the valence band offset was 0.2 ± 0.3 eV. This result indicates that the conduction-band offset at the In0.17Al0.83N/GaN interface is large, i.e., 0.9 to 1.0 eV, and occupies a large part of the entire band discontinuity.

Published
2010

44. Small valence-band offset of In0.17Al0.83N/GaN heterostructure grown by metal-organic vapor phase epitaxy

Author

1000030212400, Akazawa, M., Matsuyama, T., Hashizume, T., Hiroki, M., Yamahata, S., Shigekawa, N., 1000030212400, Akazawa, M., Matsuyama, T., Hashizume, T., Hiroki, M., Yamahata, S., and Shigekawa, N.

Abstract

The valence-band offset of a lattice-matched In0.17Al0.83N/GaN heterostructure grown by metal-organic vapor phase epitaxy (MOVPE) was investigated by x-ray photoelectron spectroscopy (XPS). Atomic force microscopy and angle-resolved XPS indicated that a thin In0.17Al0.83N (2.5 nm) layer was successfully grown by MOVPE on GaN. The XPS result showed that the valence band offset was 0.2 ± 0.3 eV. This result indicates that the conduction-band offset at the In0.17Al0.83N/GaN interface is large, i.e., 0.9 to 1.0 eV, and occupies a large part of the entire band discontinuity.

Published
2010

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