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States in the Gap of Doped and Undoped a-Si:H Studied by Photomodulation Spectroscopy

Published online by Cambridge University Press:  26 February 2011

T. X. Zhou
Affiliation:
Division of Engineering and Department of Physics Brown University, Providence, Rhode Island 02912
Z. Vardeny
Affiliation:
Division of Engineering and Department of Physics Brown University, Providence, Rhode Island 02912
J. Tauc
Affiliation:
Division of Engineering and Department of Physics Brown University, Providence, Rhode Island 02912
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Abstract

The steady state photomodulation spectrum, its temperature and excitation intensity dependences have been studied in phosphorous doped and undoped a-Si:H. The spectra are analyzed in terms of photocarriers trapped in band-tail states and dangling bonds (DB) defects in undoped samples and impurities and charged DB states introduced by doping in P-doped samples. In undoped a-Si:H we found that the two DB energy levels D± are symmetrically located about midgap with an effective correlation energy Ueff of 0.6±0.2eV. In P-doped a-Si:H D is pushed toward midgap by about 0.25 eV and Ueff = 0.4±0. 2 eV.

Type
Research Article
Copyright
Copyright © Materials Research Society 1987

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