Tesi di dottorato di ricerca
Modeling and fabrication of nanoelectronic devices based on AlGaAs/GaAs heterostructures
Settore scientifico disciplinare
Corso di studi
tutor Prof. Macucci, Massimo
- mesoscopic devices
- tunneling enhancement effect
- Fano factor
Data inizio appello
Data di rilascio
Mesoscopic physics has been a very active field of research in last decades. This is mainly due to the rapid development of fabrication techniques, which led to the realization of sub-micron devices.<br>In this thesis, numerical investigation of mesoscopic devices based on the AlGaAs/GaAs heterostructure defined by a realistic potential profile has been performed. We start with a numerical study of the robustness of the tunneling enhancement effect in a cavity to non-idealities. We show that gates with edge roughness have a negligible influence, and also that lithographic errors can be compensated, while the effect of randomly located ionized dopants is relevant, thus requiring heterostructures with very high-mobility.<br>Then transport and noise properties of realistic cascaded tunnel barriers are investigated. We find that strong localization dominates the transport through the device, even in the presence of gates with edge roughness, and the Fano factor does not approach, increasing the number of barriers, the 1/3 diffusive limit. The layout for a tunable mesoscopic cavity that allows to probe the conductance and noise properties of ``direct processes'' is also presented. Results demonstrate how the variation of different gate voltages in the cavity leads to characteristic signatures of such non-universal processes.<br>Finally, the fabrication process for the realization of a QPC is presented. Several process step have been completely developed from scatch, such as the optical lift-off and the RTA, whereas others have been calibrated for our purposes.
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