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Title:Three-dimensional field-effect transistors with top-down and bottom-up nanowire-array channels
Author(s):Chabak, Kelson D
Director of Research:Li, Xiuling
Doctoral Committee Chair(s):Li, Xiuling
Doctoral Committee Member(s):Rogers, John A; Dallesasse, John; Feng, Milton
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):nanowire transistor
High-electron-mobility transistor (HEMT)
Fin field effect transistor (finFET)
vapor-liquid-solid
gallium oxide
Metal–oxide–semiconductor field-effect transistor (MOSFET)
wrap-gate
Abstract:This dissertation research effort explores new transistor topologies using three-dimensional nanowire (NW)-array channels formed by both bottom-up and top-down synthesis. The bottom-up NW research centers on the Au-catalyzed planar GaAs NW assembly discovered at the University of Illinois Urbana-Champaign (UIUC). The top-down NW research approach involves plasma etching of an emerging wide-bandgap material, Gallium Oxide (Ga2O3), to make arrays of NW channels (or fins) for high-power electronics. Bottom-up AlGaAs/GaAs heterostructure core-shell planar NWs are demonstrated on a wafer scale with excellent yield. Their placement is determined by lithographically patterning an array of Au seeds on semi-insulating GaAs substrate. The GaAs NWs assemble by lateral epitaxy via a vapor-liquid-solid mechanism and align in parallel arrays as a result of the (100) GaAs crystal plane orientation; then, a thin-film AlGaAs layer conforms to the GaAs NWs to form AlGaAs/GaAs NW high-electron mobility channels. Radio frequency (RF) transistors are fabricated and show excellent dc and high-frequency performance. An fmax > 75 GHz with < 2 V supply voltage and ION/IOFF > 104 is measured which is superior compared to carbon-based nanoelectronics and “spin-on III-V NWs”. A comprehensive small-signal model is used to extract the contributing and limiting factors to the RF performance of AlGaAs/GaAs NW-array transistors and predict future performance. Finally, a process is developed to show that III-V NWs on sacrificial epitaxial templates can be transferred to arbitrary substrates. Top-down NWs were formed from Sn-doped Ga2O3 homoepitaxially grown on semi-insulating beta-phase Ga2O3 substrates by metal-organic vapor phase epitaxy. First, conventional planar transistors were fabricated from a sample set to characterize and understand the electrical performance as a function of Sn-doping and epitaxial channel thickness. Second, the high-critical field strength was evaluated to highlight the benefit of using Ga2O3 as a disruptive technology to GaN and SiC. Lastly, the planar transistor results feed into a design for a top-down NW-array transistor. The Ga2O3 NW-arrays were formed by BCl3 plasma etching. A new wrap-gate transistor demonstrates normally-off (enhancement-mode) operation with a high breakdown voltage exceeding 600 V which is superior to any transistor using a 3D channel.
Issue Date:2016-11-09
Type:Thesis
URI:http://hdl.handle.net/2142/95466
Rights Information:Copyright 2016 Kelson Dean Chabak
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12


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