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Explanation of the Anomalously Large Defect-Optical-Absorption Energies in Doped Amorphous Silicon

Published online by Cambridge University Press:  25 February 2011

Howard M. Branz
Howard M. Branz*
Affiliation:
Solar Energy Research Institute, Golden, CO 80401
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Abstract

The longstanding controversy over the anomalously large subgap optical absorption energies in n-type (1.1 eV) and p-type (1.3 eV) hydrogenated amorphous silicon (a-Si:H) is described and resolved. Adler suggested that these large values are incompatible with a positive effective correlation energy of the dangling bond defect and a 1.7 eV bandgap. Kocka proposed that dopant-defect pairing deepens each dangling bond transition energy by about 0.5 eV in doped a-Si:H. I assume no deepening due to pairing, a positive correlation energy of 0.2 eV consistent with the observation of dark electron spin resonance in undoped a-Si:H, and dangling-bond relaxation energies of 0.2 to 0.3 eV which are indicated by previous theoretical and experimental work. The postulate of vertical optical transitions then reduces the anomaly from about 0.9 eV to 0.4 eV. This residual anomaly may be explained by electronic-level deepening in doped a-Si:H caused by disorder-induced potential fluctuations of 0.2 eV half-width.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 149: Symposium E – Amorphous Silicon Technology - 1989 , 1989 , 119
Copyright
Copyright © Materials Research Society 1989

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References

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