ISBN 978-3-8439-2582-2

978-3-8439-2582-2, Reihe Elektrotechnik

Jan van den Hurk
Germanium Sulphide Based Resistive Switching Devices

151 Seiten, Dissertation Rheinisch-Westfälische Technische Hochschule Aachen (2016), Softcover, B5

Zusammenfassung / Abstract

Memory architectures are subject to the same scaling trend towards higher performance, low power consumption and lower cost as well as all other electronic circuits. Redox-based resistive switching memories (ReRAM) are according to the International Technology Roadmap for Semiconductors (ITRS) the most likely replacement for today’s systems. In experiments with Ag/GeSx-based electrochemical metallisation memory cells (ECM) first promising properties with regard to possible applications in high-density memories and logic architectures were demonstrated.

In this thesis about germanium sulphide-based ECM memory cells a wide range of topics is covered from the basic thin film preparation to studies of the fundamental material properties and the switching kinetics up to practical logic and memory applications. A dedicated cluster tool for sophisticated sample preparation was developed and put into operation. In this tool germanium sulphide GeSx and silver Ag were deposited in situ by RF sputter deposition as a solid electrolyte and as an active electrode material, respectively. In the context of materials investigations the existence of an electromotive force (EMF) was proven in addition to the preferred charge transfer from the electrode material Ag towards the germanium component of the electrolyte.

The electrical characterisation brought new findings in the field of SET and RESET switching kinetics, that could be classified in comparison with an existing simulation model. A clear non-linear behaviour of the SET-time at small SET-voltages could be attributed to a nucleation limited process. For the first time also the RESET kinetics was studied in detail and a limitation by the electron transfer or through the ion migration was identified, depending on the voltage range used. The possibility of a polarity-independent RESET in ECM memory cells was also demonstrated. Relevant with respect to future applications were experiments on the physical origin and the ability to suppress the continuous dissolution of the Ag electrode into the electrolyte. When interconnecting two Ag-GeSx memory cells as a Complementary Resistive Switch (CRS) ultra fast response times could be observed in the range of 20 ns. It was also possible to demonstrate alternative readout methods with this device. As part of these activities a non-destructive readout method (NDRO) was developed that is based on a volatile resistive state (VRS).