Numerical simulations of quantum devices /
This work has been motivated by the tremendous effort toward the next generation of electron devices that will replace the present CMOS (Complementary Metal Oxide Semiconductor). Non-equilibrium Green's function formalism (NEGF) and empirical tight-binding (ETB) methods have been utilized in t...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=765105841&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | This work has been motivated by the tremendous effort toward the next generation of electron devices that will replace the present CMOS (Complementary Metal Oxide Semiconductor). Non-equilibrium Green's function formalism (NEGF) and empirical tight-binding (ETB) methods have been utilized in this dissertation. We studied the transport properties of Si/SiO₂ resonant tunneling diodes (RTDs) by employing NEGF. We analyzed the physics of electron transport in Si/SiO₂ RTDs and provided some guidelines for the fabrication of such devices by considering the effect of interface roughness scattering. Atomic scale roughness is shown to be acceptable. As the island size of the roughness increases, the peak-to-valley ratio degrades to less than 5 for 1 nm roughness and less than 2 for 2 nm roughness. By the ETB method we calculated electronic and optical properties of the relatively new Si/BeSe₀₄̣₁Te₀₅̣₉ system, more precisely Si/BeSe₀₄̣₁Te₀₅̣₉ [001] superlattices (SLs). Two interface bands were found in the band gap of bulk silicon. They were related to the polar Si/BeSe₀₄̣₁Te₀₅̣₉ interface. In addition, numerical calculations showed that the optical gap is close to the fundamental gap of bulk Si and the transitions are optically allowed. Two more aspects have been studied with NEGF: intrinsic bistability and off-zone center current flow of electrons in the RTD. We showed that broadening of the quasi-bound state in the emitter by scattering reduces intrinsic bistability. So far in different theoretical papers dealing with intrinsic bistability, only the scattering in the well has been considered. Finally, we demonstrated that scattering induces off-zone center current flow of electrons in RTDs. In RTDs electrons usually have a zone-center current flow. This is due to the coherent transport for which Tsu-Esaki formula is valid. On the contrary, holes have off-zone-center current flow. We show that, generally, carrier current flow is off-center, which means that the hole behavior is extended to electrons and is related to the breakdown of the Tsu-Esaki formula. Oblique flow is due to incoherent scattering represented by interface roughness and acoustic phonons. This is a quite new result and has been recently seen experimentally for hole transport. |
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| Item Description: | Vita. "Major Subject: Physics". |
| Physical Description: | xv, 163 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 148-154). |