Investigation of Stable Amorphous Chalcogenides and Electronic Threshold Switching for Selector Only Memory

Abstract

This thesis presented a comprehensive investigation into the formation, stabilization, and threshold switching behavior of amorphous chalcogenides to develop reliable selector only memory (SOM) devices. The study first examined elemental tellurium (Te) to identify the intrinsic defect-mediated electronic processes underlying threshold switching, demonstrating that amorphous Te can be transiently stabilized through electrothermal quenching but remains thermally unstable at room temperature. Motivated by these limitations, multi-component GeSeTe alloys SOM devices were fabricated and electrically characterized to establish composition property relationships within the amorphous network, revealing material regimes that support stable LVS/HVS separation (~2.0 V/~2.8 V), enhanced endurance (106 cycles), and tunable threshold voltages (HVS for 2.8 V to 3.5 V). Material analyses, including Raman spectroscopy, XPS, UV-VIS-NIR, and XRD, further clarified how the bonding environment and structural disorder evolve with alloy composition and contribute polarity dependent Vth shift. Finally, indium incorporation was shown to effectively suppress threshold voltage drift by forming stable In-Se bonding configurations and modifying the trap landscape, resulting in improved long-term retention and reduced variability (LVS drift coefficient: 6.29 mV/dec). Overall, the findings provide experimentally grounded guidelines for engineering amorphous chalcogenides with controlled trap states and robust electronic switching, enabling high stability SOM device technologies.