h1

TY  - THES
AU  - Sommer, Nils
TI  - Modeling and simulation of bilayer area-dependent valence change memory devices
PB  - Rheinisch-Westfälische Technische Hochschule Aachen
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2024-06154
SP  - 1 Online-Ressource : Illustrationen
PY  - 2024
N1  - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University
N1  - Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2024
AB  - The development of future semiconductor devices brings major challenges. Moore's famous law has predicted the miniaturization for decades. However, current technologies are reaching their physical limits. Further, the increasing number of computer technologies worldwide requires more and more electrical energy. Therefore, new concepts are proposed, e.g., Redox-based Random Access Memory (ReRAM), in-memory computing or neuromorphic applications. In this context, valence change memory cells (VCM) are promising candidates for the implementations of these concepts. Area-dependent switching VCM cells are a special type of VCM cells. Many of the area-dependent VCM cells consist of a bilayer structure, i.e., there are two semiconducting metal-oxide layers in between two metal electrodes. The resistance of an area-dependent device scales linearly with the device area. In addition, the resistance of the VCM cell can be manipulated by applying a voltage stimuli to the electrodes. It was shown experimentally that there is an exchange of oxygen ions between the two metal-oxide layers when the resistance of the device is changed. Hence, it was suggested that this exchange is the fundamental reason for the resistance change. However, this idea has been barley tested by physically models so far. In this work, two physically motivated models for area-dependent bilayer VCM cells are developed. Both models incorporate the idea of an oxygen exchange between the two metal-oxide layers. By means of these models, the influence of an oxygen exchange on the device resistance is investigated. Under special interest is the influence of different materials parameters on the resistance change as well as on the dynamically movement of the oxygen ions. It is shown that device resistance can be changed by the oxygen exchange. Thereby, the behavior of the resistance change depends on how far the oxygen ions migrate into the bulk of the materials. Further, a dependency on the material permittivities is shown. Another property of area-dependent VCM cells is that the resistance changes gradually under applied voltages. By means of the developed models it is investigated what is necessary to gain a gradual change of the resistance. Furthermore, the models are used for a detailed analysis of the movement of the oxygen ions and how the charge carriers, i.e., electrons and holes, overcome a tunnel barrier that is created by one of the oxide layers. At the end of this work, the simulation results are compared to experimental measurements from the literature to identify which measured effects can be explained by the models. In addition, it is discussed which effects cannot be explained by the model of a simple oxygen exchange and which extension on the models are necessary.
LB  - PUB:(DE-HGF)11
DO  - DOI:10.18154/RWTH-2024-06154
UR  - https://publications.rwth-aachen.de/record/988396
ER  -