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Investigation and Modeling of Impact Ionization Spatial-Transient Effects in Silicon Devices

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What
  • PhD Defenses
When Aug 27, 2012
from 10:00 AM to 11:30 AM
Where ENGR. IV Bldg., Faraday Room 67-124
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Quan Chau

Advisor: Dee-Son Pan

 

Abstract:

Impact ionization (II) has played an important role in semiconductor devices; yet its understanding has not been mature. Existing models are not rigorously applicable to explaining II in different device structures and different operational regimes. Monte Carlo (MC) programs simulating transport of both electrons and holes are developed to investigate II in homogeneous electric field and in scaled devices. Impact ionization is modeled as a positive feedback loop in which electrons create holes and the secondary holes feedback secondary electrons. The positive feedback loop enables successful simulations of the II process in which both electrons and holes participate simultaneously. From the MC simulation results, a pseudo-local electric field model and the positive feedback model are proposed and proven to be sufficient in predicting the II current gain in short devices. In addition, an analytical formula of the substrate current in sub-micrometer MOSFETs is successfully derived.

The newly-developed formula is able to explain different abnormal behaviors of the substrate current that cannot be explained by the conventional formula.

 

Biography:

Quan Chau received his B.S. degree and M.S. degree in Electrical Engineering at UC Berkeley and UC Los Angeles, respectively.

He is currently a Ph.D. candidate in Electrical Engineering at UC Los Angeles under the advisory of Professor Dee-Son Pan. His current research focuses on modeling impact ionization in short silicon devices and studying its applications in DRAM and THz source devices.

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