Browsing by Author "Esmaeili-Rad, Mohammad R."
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- Photo-induced instability of nanocrystalline silicon TFTsPublication . Bauza, Marius; Ahnood, Arman; Li, Flora; Vygranenko, Yuri; Esmaeili-Rad, Mohammad R.; Chaji, G.; Sazonov, Andrei; Robertson, John; Milne, William; Nathan, ArokiaWe examine the instability behavior of nanocrystalline silicon (nc-Si) thin-film transistors (TFTs) in the presence of electrical and optical stress. The change in threshold voltage and sub-threshold slope is more significant under combined bias-and-light stress when compared to bias stress alone. The threshold voltage shift (Delta V-T) after 6 h of bias stress is about 7 times larger in the case with illumination than in the dark. Under bias stress alone, the primary instability mechanism is charge trapping at the semiconductor/insulator interface. In contrast, under combined bias-and-light stress, the prevailing mechanism appears to be the creation of defect states in the channel, and believed to take place in the amorphous phase, where the increase in the electron density induced by electrical bias enhances the non-radiative recombination of photo-excited electron-hole pairs. The results reported here are consistent with observations of photo-induced efficiency degradation in solar cells.
- Vertical CNT-Si Photodiode ArrayPublication . Ahnood, Arman; Zhou, Hang; Dai, Qing; Vygranenko, Yuri; Suzuki, Yuji; Esmaeili-Rad, Mohammad R.; Amaratunga, Gehan; Nathan, ArokiaA photodiode consisting of nanopillars of thin-film silicon p-i-n on an array of vertically aligned carbon nanotubes (CNTs) with a noncontinuous cathode electrode is demonstrated. The structure exploits the intrinsic enhancement of the CNTs' electric field, which leads to reduction in the photodiode's operating voltage and response time and enhancement of optical coupling due to better light trapping, as compared with the conventional planar photodiode. These improvements translate to higher resolution and higher frame rate flat-panel imaging systems for a broad range of applications, including computed tomography and particle detection.