Abstract
The effects of photo-related stress on the electrical
performances of a-SiGe:H thin-film transistors (TFTs) were investigated in
comparison with a-Si:H TFTs. Compared with a-Si:H TFTs, the a-SiGe:H TFTs
show better stability to the light stress because the number of electrons
involved in the creation of dangling bonds are smaller in a-SiGe:H TFTs, resulting
in less light-induced degradation. However, a larger threshold voltage shift
from the positive gate bias was observed due to the higher number of weak
bonds in a-SiGe:H TFTs, which leads to a higher gate bias instability than
is observed for a-Si:H TFTs. The temperature dependences of the electrical
properties in a-SiGe:H TFTs were observed, and they indicated that a-SiGe:H
TFTs follow a thermally activated behavior pattern. Based on the thermally
activated behavior, a new model predicting the lifetime of a-SiGe:H TFT image
sensors was proposed. The instability of the drain current with respect to
the stress time under an electrical bias and light was estimated. Based on
the calculated lifetime, the a-SiGe:H TFTs are predicted to be reliable for
long-term applications in image sensors.
© 2012 IEEE
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