教員・研究者詳細 - 梅津　郁朗

Photothermal deflection (PD) signals without applied bias are a direct observation of nonradiative recombination processes of photoexcited carriers, which strongly correlate with photocurrent under applied bias. The PD signal under DC bias was carefully compared with the photocurrent (PC) signal in the energy region around and above the band gap. A large dip, which was not observed in PC spectra, was observed in PD spectra in the spectral region near the absorption edge. This spectral feature was discussed from the standpoint of Joule heat due to drift of photocarriers. We have pointed out that dark Joule heat (W-d) and effective applied voltage (V-s) are important in analysis. By taking into account these parameters, the experimental spectrum of PD signals under DC bias was successfully reproduced. It is concluded that variation of V-s which arises from large photosensitivity causes a dip in PD spectra. No evidence of the photon energy dependence of the recombination process was observed in PD spectra.

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DEPLETION LAYER WIDTH IN UNDOPED A-SI-H SCHOTTKY-BARRIER REVEALED BY REVERSE BIAS PHOTOCURRENT

K MAEDA, W CHIYODA, UMEZU, I, A KUROE

JOURNAL OF APPLIED PHYSICS 75 ( 7 ) 3522 - 3529 1994年4月

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出版者・発行元：AMER INST PHYSICS

Reverse bias photocurrent of undoped a-Si:H Schottky barrier was investigated under excitation with uniformly absorbed light. Dependence of the photocurrent on the applied voltage V gives unambiguous dependence of the depletion layer width W on voltage V, which cannot be obtained by conventional capacitance-voltage measurements for undoped a-Si:H. There are two voltage ranges giving parabolic dependence of W with different apparent ionized donor densities due to a spatial variation of the space-charge density. These observations are considered to be characteristic of semiconductors with major deep gap states of large energy width. The experimental results were analyzed using a simple model of energy distribution of the gap state density of dividing the depletion layer into two. In one of these deep depletion occurs. The variation of the apparent W-V relation observed upon lowering the exciting photon energy was analyzed to be related to a decrease in the absorption coefficient with the applied voltage due to an emptying of the initial states of the gap state absorption. Results of the analysis are consistent with the electron-spin density observed in the same undoped a-Si:H.

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Analysis of joule heat in a-Si:H film by photothermal deflection spectroscopy

Ikurou Umezu, Keiji Maeda

Japanese Journal of Applied Physics 33 ( 10R ) 564 - 561 1994年

共著

Photothermal deflection (PD) signals without applied bias are a direct observation of nonradiative recombination processes of photoexcited carriers, which strongly correlate with photocurrent under applied bias. The PD signal under DC bias was carefully compared with the photocurrent (PC) signal in the energy region around and above the band gap. A large dip, which was not observed in PC spectra, was observed in PD spectra in the spectral region near the absorption edge. This spectral feature was discussed from the standpoint of Joule heat due to drift of photocarriers. We have pointed out that dark Joule heat (W d) and effective applied voltage (V S) are important in analysis. By taking into account these parameters, the experimental spectrum of PD signals under DC bias was successfully reproduced. It is concluded that variation of V S which arises from large photosensitivity causes a dip in PD spectra. No evidence of the photon energy dependence of the recombination process was observed in PD spectra. © 1994 IOP Publishing Ltd.

DOI： 10.1143/JJAP.33.5647

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INTERFACE STATE DENSITY OF SINX-H/C-SI MIS STRUCTURE

MAEDA K, JINNAI T, UMEZU I

JOURNAL OF NON-CRYSTALLINE SOLIDS 166 849 - 852 1993年12月

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