On the fundamental absorpion of amorphous semiconductors
The present thesis reviews different models that describe the fundamental absorption of amorphous semiconductors. These models make use of the electronic density of states to shape the absorption coefficient in the fundamental absorption region. The study focuses on the optical absorption of hydr...
| Autor Principal: | Angulo Abanto, José Rubén |
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| Formato: | info:eu-repo/semantics/masterThesis |
| Idioma: | Español |
| Publicado: |
Pontificia Universidad Católica del Perú
2016
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| Materias: | |
| Acceso en línea: |
http://tesis.pucp.edu.pe/repositorio/handle/123456789/7000 |
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| Sumario: |
The present thesis reviews different models that describe the fundamental absorption of
amorphous semiconductors. These models make use of the electronic density of states to
shape the absorption coefficient in the fundamental absorption region. The study focuses
on the optical absorption of hydrogenated amorphous Silicon (a-Si:H), hydrogenated and
non-hydrogenated amorphous silicon carbide (a-SiC:Hx), and silicon nitride (a-SiN) thin
films. On the one hand, parameters like the Tauc-gap and Urbach energy are obtained from
the absorption coefficient using the traditional models. On the other hand, a recently
proposed model based on band thermal fluctuations was assessed [1]. This model allows a
determination of the mobility gap and the Urbach energy from a single fit of the absorption
coefficient without the need of identifying the Tauc region beforehand. Furthermore, it is
able to discriminate the variation of the Urbach energy from the bandgap. The results
allow the evaluation of the aforementioned parameters with annealing treatments at
different temperatures. The mobility edges are insensitive to the structural disorder by at
least one degree lower than the Urbach energy. This work demonstrates that it is possible
to obtain the mobility edge through this model. In addition, the measured Tauc-gap and
Urbach energy exhibit a strong linear correlation following the Cody model for all three
materials. Finally, the Urbach focus concept is evaluated and estimated under different
analysis. |
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