NONEQUILIBRIUM CARRIERS IN A-SI-H EXCITED BY DEFECT ABSORPTION

TitleNONEQUILIBRIUM CARRIERS IN A-SI-H EXCITED BY DEFECT ABSORPTION
Publication TypeJournal Article
Year of Publication1993
AuthorsSaleh, R., I. ULBER, W. FUHS, and H. MELL
JournalJournal of Non-Crystanlline Solids
Volume166
Pagination563-566
Date PublishedDEC
Type of ArticleProceedings Paper
ISSN0022-3093
Abstract

We have used light-induced electron spin resonance (LESR) and photoluminescence (PL) to examine the energetic and spatial distribution of non-equilibrium carriers in a-Si:H excited with monochromatic light of 1.16 to 1.96 eV at T=20 K. The LESR spectra and the observation of intrinsic PL for excitation with hv < 1.4 eV reveal that efficient generation of both electrons and holes occurs by defect absorption. However, the quantum efficiency of the intrinsic PL is smaller by about one order of magnitude while that of the defect PL is larger by a factor of 5 compared to excitation with hv > 1.5 eV. This is attributed to the fact that not only carrier creation but also most of the recombination occurs through the defect levels. Our LESR data suggest a very similar ratio of band-tail electrons and holes, namely 0.4, for excitation with 1.16 and 1.96 eV photons, respectively. We believe that this result argues against the existence of a significant density of charged defects in undoped a-Si:H films.

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