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Evaluation of the steady‐state photocarrier grating technique with respect to A‐Si: H and its application to A‐Si 1–X Ge X : H alloys
Author(s) -
Abel C.D.,
Bauer G. H.
Publication year - 1993
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.4670010403
Subject(s) - ambipolar diffusion , electric field , grating , electron , charge carrier , materials science , condensed matter physics , diffusion , photoconductivity , relaxation (psychology) , dielectric , optoelectronics , physics , thermodynamics , psychology , social psychology , quantum mechanics
The steady‐state photocarrier grating technique is analysed with respect to deviations from local charge neutrality. We present a generalized expression for the normalized photoresponse β as a function of the grating period as well as of the external electric field; the transport is characterized in the sense of bipolar and ambipolar, diffusion and drift displacement, respectively. Experimental data for undoped a‐Si: H, especially the variation of the β coefficient with the external electric field, are discussed and fitted by the generalized equation. the effective dielectric relaxation time, which takes the trapped photogenerated majority carriers into account, is found to be responsible for ambipolar transport in undoped a‐Si: H in the low electric field regime. Further, the μτ‐products of electrons and holes in a‐Si 1‐x Ge x : H alloys are deduced experimentally. the low‐gap alloys are an appropriate candidate for photovoltaic applications.