Phase Change Material Based Ohmic Switches for Reconfigurable RF Applications

Abstract

This research work is focused on the study and development of chalcogenide phase change materials and their applications in reconfigurable RF modules and systems. Germanium telluride (GeTe), one of the chalcogenide phase change materials, is studied and used in the development process of RF ohmic switches. This thesis presents the study of GeTe and other phase change materials, the design, fabrication and measurements of GeTe phase change material based RF switches, and the performance evaluation as well as the operation and breakdown analysis of the GeTe phase change RF switches. It also discusses the potential applications of GeTe RF switches in reconfigurable RF modules by demonstrating a bandpass filter design.

RF switches based on solid-state transistors and diodes, and micro-electromechanical system (MEMS) as well as other technologies have been reported and used in integrated circuits and systems for RF and microwave applications. Each of these technologies for RF switches shows some limitations regarding RF performance, integration compatibility, cost, fabrication yield, or reliability. This thesis presents a novel alternative for RF switch development using GeTe phase change material. The special phase transition properties of phase change materials have drawn attention for decades. Material study and characterization of phase change materials have been performed for a better understanding of their properties. Phase change materials have since been developed for different applications, with non-volatile memory modules being the most successful application. With the success in phase change memory design, we have directed our attention to RF switching applications based on phase change materials. Two main types of GeTe phase change material based RF ohmic switches are developed and the design and fabrication of each is discussed in detail. The RF switches designed using GeTe have shown very competitive performance results compared to other existing RF switch designs. Analysis and modeling of the switches have also been performed for a better understanding of the devices and phase change materials as well as their phase transition process. A reconfigurable bandpass filter using GeTe switches have verified the good functionality of phase change RF switches and their promising potential in reconfigurable RF applications.