Ressonância paramagnética em germânio amorfo hidrogenado e silício microcristalino hidrogenado

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

In this thesis, we present for the first time light-induced electron spin resonance, LESR, measurements in a-Ge:H. The signal consists of two different centers: 1) assigned to electrons trapped in conduction band tails; and 2) holes trapped in valence band tails. We also have performed a recombination kinetics study based on the LESR time response. We have found that the process is mainly due to distant-pair recombination in a way very similar to that one reported for a-Si:H. ESR and LESR measurements were also performed in mc-Si:H. An alternative interpretation for the resultant spectra was given. The signal, which appears in the dark, was reproduced using a powder pattern simulation of a single center with axial symmetry. The values found to the g tensor are g// = 2.0096 e g^ = 2.0031. This center seems to be related with defects in the crystal phase instead of dangling bonds (as suggested before). The LESR signal, on the other hand, is explained by a sum of two different centers: 1) related with electrons in conduction band tails; and 2) related with holes in valence band tails. Finally, a series of boron doped hydrogenated amorphous silicon, a-Si:H(B), prepared by rf-co-sputtering, was investigated. The variation obtained in the activation energy and room temperature conductivity was about the same reported for samples prepared by other techniques. However, since our sample has a much higher amount of dangling bonds, we need to incorporate a much higher amount of boron, in order to shift the Fermi level noticeable. As a consequence, the production of dangling bonds due to doping does not follow the same trend of PECVD samples. In our case, it is related with the disorder produced by the introduction of the large amount of boron in the network in instead of been related with the incorporation of charged impurities.

ASSUNTO(S)

filmes semicondutores ressonancia paramagnetica eletronica semicondutores amorfos

ACESSO AO ARTIGO

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