Photon-Assisted Electron Tunneling in Metal-Insulator-Metal Rectenna Structures

Date of Award

2022

Degree Name

Ph.D. in Electro-Optics

Department

Department of Electro-Optics

Advisor/Chair

Partha Banerjee

Abstract

Quantum physics has had a remarkable development since the last century. We study novel metal-insulator-metal structure configurations for finding broadband and ultrafast response photodetectors and alternative choices to conventional solar cells. If two dissimilar electrodes are separated by an insulator that is sufficiently thin, electrons can tunnel through the gap region by means of quantum tunneling. Electron tunneling through the insulating gap is driven by a bias voltage or an electromagnetic field. The resulting electrical current is described using the photon-perturbation tunneling model. For the right choice of materials, the tunneling current can be asymmetric and there is a net rectified current through the insulator junction. Due to this property, the devices have been called rectennas and many experiments have been performed in the radio frequency regime. More recently rectenna experiments have been extended in the near-infrared regime. Semiconductor diodes have many imperfections such as heat problems and relatively slow response, while metal-insulator-metal devices have less heat problem issues and have response time of carriers in the order of femtoseconds, which can be faster than the period of oscillation of the electromagnetic field. We have applied the transfer matrix method and the Wentzel, Kramers, Brillouin approximation to solve the Schro?dinger equation to find the electron tunneling probability and to predict the current-voltage characteristics of a metal-insulator-metal structure. This, along with the density of states, the Fermi occupation probability, and the quantum confinement effect is used to derive the dark current density for the metal-insulator-metal diode. The illuminated current-voltage characteristics is described by the photon-perturbation theory at high optical frequencies. Upon combining classical and semiclassical pictures of photodetection, a photon-perturbation tunneling model is presented, to fully uncover the interaction between electron and photon field. The electrons are excited and quantized as quasi-particles, this phenomenon is the so-called quantum effect. We validate the theory for dark current and illuminated current with experiments with the goal of calculating the current responsivities. Metal-insulator-metal Au-TiO2-Ti diodes are designed and fabricated in-house using photolithography, along with electron beam evaporation and sputter depositions. Further research is needed to develop metal-insulator-metal devices into practical solar energy harvesters.

Keywords

Engineering, Physics, quantum tunneling, photon-assisted tunneling, photodetection, solar cell

Rights Statement

Copyright © 2022, author

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