Oxides on Semiconductors for Novel Device Applications
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Oxide materials possess unique functionalities which when combined with semiconductors will enable a variety of novel device applications. They have properties that include high dielectric constant, ferromagnetism, and ferroelectricity. This research will focus on two major topics: (a) Materials/structure optimization of CaCu3Ti4O12/LiNbO3 (CCTO/LNO-Dielectric/Ferroelectric) based Voltage Controlled Capacitors (varicaps) and (b) deposition of ferroelectrics on III-V semiconductors or compound semiconductor based devices. Varicaps are electronic components with a capacitance that is tunable using a DC bias signal. The DC tunable dielectric constant of ferroelectric materials makes them a potential candidate for varicap applications. The frequency-dependent dielectric constant is a drawback for ferroelectric varicaps. This research investigates the frequency dependence of ferroelectric-based varicaps in combination with a large dielectric constant capacitor through the optimization of film deposition process and/or structures. Integration of ferroelectric oxide materials with high mobility III-V semiconductors is an attractive research topic albeit challenging due to the dissimilarity of the systems. The deposition and characterization of Pb(ZrxTi1-x)O3 (PZT) ferroelectrics on GaAs substrates is addressed in this research. The issue of gallium and arsenic diffusion and their reaction with lead atoms is mitigated using a buffer layer and employing a novel modified pulsed laser deposition technique to deposit the PZT films directly on GaAs/STO substrate.