Date of Award

Spring 5-2018

Embargo Period

5-21-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering

Advisor(s)

Jim Bain

Second Advisor

Jeyanandh Paramesh

Abstract

The goal of any switch is to enable reconfiguration, flexibility, or adaptability for the network in which it is being implemented. Electrical switches that operate at radio frequencies (RF) are designed to increase system functionality and flexibility, such as routing signals to different locations or changing the frequency response of a circuit. Unfortunately, current state-of-the-art (SOA) RF switches do not have the performance, size, or cost in order to enable the large scale flexibility seen in modern digital system-on-chips (SoCs) and FPGAs. Non-volatile chalcogenides present a unique opportunity to create analog SoCs, as low loss, low power consumption, small size, and low cost integration are all simultaneously achievable in this material system. This thesis details the first demonstration, performance, and integration of 4-terminal, indirectly heated phase-change switches for reconfigurable RF systems. The first demonstration of device functionality outperformed SOA FET-based RF switches in terms of frequency performance (1.1 THz Fco, or 145 fs Ron*Coff), and was improved by over an order of magnitude over the course of this research (12.5 THz Fco, or 12.7 fs Ron*Coff). The investigations into power handling have resulted in an extracted threshold field of 12.6 V/μm in 50:50 GeTe, an improvement in OFF-state power handling from 18 dBm to 29 dBm, and a switch with a simultaneous Ron, Coff, Fco, Vth, PRFmax,off, and reliability of 1.2 Ω, 12.3 fF, 10.6 THz, 6 V, 28 dBm, and >500,000 cycles, respectively. A correlation between the DC Vth and the RF power handling was demonstrated, identifying the fundamental mechanism for power handling limitations. Three different reconfigurable RF system prototypes were fabricated using heterogeneous integration of these phase-change switches with a multifunction SiGe BiCMOS MMIC. Problems with the RF performance of the system highlighted the need for an improved integration of these phase-change switches. A back-end-of-line (BEOL), CMOS-compatible monolithic integration process was then experimentally demonstrated for the first time, detailing the benefits of future monolithically integrated phase-change switches on a variety of semiconductor technologies.

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