| Date |
Do, 19.03.2015 - Do, 19.03.2015 |
| Time |
11.15 |
| Speaker |
Dr. Antonino La Magna, CNR IMM, Istituto per la Microelettronica e Microsistemi, Catania, Italy |
| Location |
Universität Bern, Institut für Angewandte Physik, Gebäude exakte Wissenschaften, Hörsaal B116, Sidlerstrasse 5, 3012 Bern |
| Program |
We review the formalism and the associated computational methods applied to the theoretical investigations of electronic transport in different regimes: From the quantum coherent to the semi-classical regimes, from the low to the high field regimes. The various conditions are characterized by device feature size, electrons energy distribution and transient response. Independently of the level and accuracy of the theory two necessary requirements are: a) the adequate description of the electronic structure of the studied systems and b) the self-consistent coupling with a Poisson solver for the evaluation of the electric field due to the external bias. The calculations of quantum transport rely on non-equilibrium Green's function formalism, where the estimate of the electronic structure is an inner part of the computation; whilst semi- classical schemes derived from the Boltzmann equation represent reliable approaches when quantum effects can be neglected. Particular examples of applications will be discussed for the case graphene based device (quantum transport) and the electron kinetics in semiconductors device under THz excitation at high electric field strength (semi-classical quasi- ballistic transport). In the first case, by varying both the width and the length of two-terminal devices from the nano- to the micro-scale, we discuss localization, pseudo-gap formation, transport length scales and conductance characteristics for variable defect/impurity concentrations. Ensemble Monte Carlo method can accurately simulate the semiconductor device features for transient electric field with strengths up to several hundred of kV/cm and device with feature length scale significantly larger than 10nm. Among the different scattering mechanisms carrier generation has to be consistently included in the computational model. Moreover, matter migration due to the hot electrons effects should be evaluated in order to understand observed permanent modifications of the device materials in operation conditions. |
| Download |
 (75 KB) |
|
(75 KB) |
| Link |
www.iap.unibe.ch |
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