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Study of wide bandgap semiconductor nanowire field effect transistor and resonant tunneling device

Shao, Ye
http://orcid.org/0000-0002-7707-2462
http://rave.ohiolink.edu/etdc/view?acc_num=osu1448230793

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
The history of the semiconductor industry is a story of Moore's Law. However, the end of Moore's Law has been predicted for the near future as the transistor’s overly-scaled gate length eventually loses control of current flow in the channel. Gate-all-around transistors with one-dimensional nanowires (NWs) as the device channel surrounded by a gate to control the flow of current are considered as one of potential candidates for next generation electronics. In addition, their unique properties also make NW an ideal candidate for resonant tunneling devices (RTDs) with extremely high switching speed (in terahertz range) for future high frequency and THz communications. Before this becomes a reality, however, unless some fundamental issues of semiconductor NWs are clarified, it is hard to realize breakthroughs on device performance. This Ph.D research aims to address some of these issues. The research highlights and key innovations are summarized as below: 1. Metallic contacts: We show that surface states in ZnO NWs can affect the properties of metal contacts to NWs, causing Fermi level pinning with a fixed Schottky barrier height and high contact resistance. A circuit model is developed to characterize metal contacts for NW FETs. The results show that surface states in ZnO NWs is oxygen vacancy related. A general model is also developed to study interfacial traps between NWs and the gate dielectrics applied. 2. Electron transport: Our results show that the electron transport of ZnO NW FETs is governed by the space charge limited model at temperatures below a trap temperature. Above the trap temperature, the electron transport is thermionic emission dominated. A method is developed for NW trap density extraction through the Arrhenius plot. Based on the space charge limited model, we show that the conventional field effect mobility extraction method over estimates the mobility in NW FETs. An accurate method that takes into account the surface trap related scattering effect is developed. The extracted surface state scattering related mobility component also exhibits a temperature dependence. 3. Low frequency (1/f) noise (LFN) in NWs. We show that the LFN power density in GaN NWs can be effectively compressed by surface passivation. The better material quality and top gate control with the gate dielectric of atomic layer deposition (ALD) deposited Al2O3 are effective to reduce the LFN level in GaN NW FETs. The double gate-device design enables the analysis of LFN contributions from both device channel region and access region, which results in different bias dependence. Based on the extracted Hooge’s parameter values, it is suggested that more efforts need to focus on the device channel region to improve device noise performance. 4. NW RTDs: We successfully design, fabricate, and characterize AlN/GaN double barrier NW-based RTDs with a record high maximum tunneling current of 106 A/cm2. We are the first group to demonstrate the peak-to-valley current ratio of 40 for NW-based RTDs by applying one side Schottky contact device structure. Both of these properties are critical features of high performance RTDs for next generation communication applications. We are also the first group to investigate the impact of polarization effect in III-Nitrides NWs on the RTD device performance by two-dimensional quantum simulations. In this work, the concepts of GaN/InN double barrier NW-based RTDs and gate controlled NW RTDs have also been demonstrated.
Wu Lu (Advisor)
Siddharth Rajan (Committee Member)
Marvin White (Committee Member)
Haijun Su (Committee Member)
195 p.
Electrical Engineering
nanowire; ZnO; GaN; field effect transistor; low frequency noise; electron transport; space charge limited current; resonant tunneling diode;

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Citations

  • Shao, Y. (2015). Study of wide bandgap semiconductor nanowire field effect transistor and resonant tunneling device [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448230793

    APA Style (7th edition)

  • Shao, Ye. Study of wide bandgap semiconductor nanowire field effect transistor and resonant tunneling device. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1448230793.

    MLA Style (8th edition)

  • Shao, Ye. "Study of wide bandgap semiconductor nanowire field effect transistor and resonant tunneling device." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1448230793

    Chicago Manual of Style (17th edition)

osu1448230793
108
© 2015, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.