Date of Award


Document Type

Open Access Thesis


Electrical Engineering


College of Engineering and Computing

First Advisor

Grigory Simin


This work deals with novel microwave switches based on III-Nitride varactors. RF switches, power limiters and other control devices are important components of various RF systems, such as wireless modules of laptops, tablets, cell phones etc., satellites communication systems, radars, multi-band wireless and aerospace communications, phased array antennas and so worth. Traditional RF switches are fabricated using pin diodes or MEMS, Si MOSFETs or GaAs HEMTs. These devices have a number of fundamental limitations. Si or GaAs based devices suffer from a low breakdown voltage and cannot handle high RF power. Pin-diodes require large forward currents and do not allow for fast turn-on. III-Nitride heterostructures open tremendous opportunities for RF control devices due to the record high sheet electron density in the 2D channel, extremely low channel resistance, high breakdown field and excellent temperature stability. Recently, RF switches based on III-Nitride High Electron Mobility Transistors (HEMTs) have been developed and became commercially available. In this work, we studied a novel type of RF switch based on III-Nitride varactor. Unlike HEMTs, varactor uses capacitance modulation to control the flow of RF signal and offers a number of advantages over HEMTs: they allow for shorter channel, do not have gates or ohmic contacts and hence the fabrication is alignment- and anneal - free, they do not consume DC current and provide the DC block. Unlike regular varactor diodes, in this work, we analyze three-terminal varactor having independent control electrode which further enhances the switch performance. The varactor and varactor based RF switch analysis in this work is done by modeling and simulation using Synopsys Sentaurus tools as well as MATLAB. Modeling approach allows obtaining device characteristics and material dependencies that are hardly achievable in experiments, such as effect of donor and acceptor traps or achievable switching time. The obtained results are compared with available experimental data.


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