Analysis of Joule Heat in a-Si:H Film by Photothermal Deflection Spectroscopy

概要

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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 (Vs) 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 Vs 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.
社団法人応用物理学会の論文
1994-10-15