Friday, March 12, 2021

RTN in PD Dark Current Thesis

 Toulouse University publishes a PhD thesis "Defects in silicon: revisiting theoretical frameworks to guide ab initio characterization" by Gabriela Herrero-Saboya.

"In this thesis, we describe the effect of localized defects on the electronic properties of silicon. After 60 years of silicon devices production, one might expect all details of this material to be fully understood, especially considering that the manufacture of nowadays nanometer-sized transistors requires quasi-atomic accuracy. However, as a direct result of such extreme miniaturization, the accidental creation of even one single trapping center can be sufficient to alter the desired electronic properties of the sample, becoming one of the most feared phenomena in the industry. 

Atomistic numerical simulations in silicon, based on the Density Functional Theory, do however typically target specific defect-properties, not giving a complete theoretical picture of the system, often overlooking previous models and experimental evidence. In the present thesis, we provide new insight into iconic defects in silicon through the quantification of long-established atomistic models, making an explicit link with the characterization techniques. Our detailed exploration of the DFT energy surface of the silicon E-center, guided by a simple Jahn-Teller model, confirmed the observed defect-dynamics at different temperature regimes, allowing us to link the presence of such point-like defect to a burst noise in image sensors.

In section 3.2, we analyse the relevance of the silicon E-center for several technologically relevant processes, like the Dark-Current Random Telegraph Signal in image sensors. The former might be defined as a burst noise in electronic devices commonly linked to the finite-temperature dynamics of crystallographic defects, motivating an extensive exploration of the potential energy surface at different temperature regimes. Our DFT and NEB calculations, in excellent agreement with EPR spectroscopy, provide new insight into the defect dynamics, and in particular into the vacancy-mediated dopant diffusion mechanism in silicon."


  1. Yet another great work from the group of Vincent Goiffon and Pierre Magnan! Well done!

  2. Actually, even if we collaborate actively with the advisors of this thesis (with a common working group on RTS), Garbiela's thesis has been supervised by Anne Hemeryck (LAAS CNRS), Nicolas Richard (CEA-DAM) and Layla Martin-Samos Colomer (CNR-IOM). I had the pleasure to follow this work from a distance and interact with Garbiela during her PhD but I cannot say that my group is involved. I really enjoyed the defence and I'm looking forward to see the continuation of this work.


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