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Diffusion, Drift, and Recombination of Holes In a-Si:H

Published online by Cambridge University Press:  15 February 2011

R. Schwarz
Affiliation:
Physics Department E16, Technical University of Munich, D-85747 Garching, Germany
F. Wang
Affiliation:
Physics Department E16, Technical University of Munich, D-85747 Garching, Germany
S. Grebner
Affiliation:
Physics Department E16, Technical University of Munich, D-85747 Garching, Germany
Q. Gu
Affiliation:
Physics Department, Syracuse University, Syracuse, NY 13244–1130, U.S.A.
E. A. Schiff
Affiliation:
Physics Department, Syracuse University, Syracuse, NY 13244–1130, U.S.A.
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Abstract

We compare measurements in a-Si:H of ambipolar diffusion length Lamb (from steady-state photocarrier gratings (SSPG)) and hole drift Χ (t) (from time-of-flight (TOF)). Using the response time tR from small-signal photocurrent decay measurements, we find that the equation L2amb = 2 (kT/e) Χ (tR) /E is consistent with the measurements, where E is the electric field inducing hole drift in TOF. Several samples under different temperature and light intensity levels have been studied. This equation has several implications. Under the usual SSPG illumination conditions, electron-hole recombination occurs while holes are still occupying valence bandtail states; hence SSPG is not sensitive to hole capture by deep levels. Furthermore, the experiments show that the Einstein relation is valid for holes in a-Si:H. We are unaware of prior direct tests of this relation in an amorphous semiconductor.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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References

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