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Ambipolar Diffusion Coefficients in a-SiC:H Alloys in Steady- State and Transient Grating Measurements

Published online by Cambridge University Press:  01 January 1993

H. Weinert
Affiliation:
Humboldt-Universität zu Berlin, Berlin, Germany
M. Petrauskas
Affiliation:
Vilnius University, Vilnius, Lithuania
J. Kolenda
Affiliation:
Vilnius University, Vilnius, Lithuania
A. Galeckas
Affiliation:
Vilnius University, Vilnius, Lithuania
F. Wang
Affiliation:
Technical University of Munich, Garching, Germany
R. Schwarz
Affiliation:
Technical University of Munich, Garching, Germany
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Abstract

Recently we have determined surprisingly large values of the ambipolar diffusion coefficient D of 3 − 9 cm2/s in amorphous silicon-based alloys and a-Si:H/a-SiC:H multilayer structures from transient grating decays in the psec time domain. The steady-state photocarrier grating method, however, resulted in much lower D values (∼10−4 cm2/s) in the same samples. Since high carrier densities of typically 1019 cm−3 are reached in the psec domain, the Einstein relation may no longer be valid. The large diffusivity of non-equilibrium carriers decreases, however, rapidly in time due to energy relaxation and carrier recombination until a stable trap occupation under steady-state condition is reached.

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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References

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