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Scanning Probe Microscopy Measurements and Simulations of Traps and Schottky Barrier Heights of Gallium Nitride and Gallium Oxide

Galiano, Kevin
http://rave.ohiolink.edu/etdc/view?acc_num=osu1576715425331868

Abstract Details

2020, Doctor of Philosophy, Ohio State University, Physics.
Gallium Nitride (GaN) and Gallium Oxide (Ga2O3) are two semiconductors of significant interest for high power and high frequency electronics. However, the performance of these electronics can be inhibited by the presence of defects which can produce "trap" states in the "forbidden" bandgap of semiconductors. These traps can then degrade the output current of transistors and cause undesireable time-dependent phenomenon. This work investigates the physical origin of the most common trap, EC - 0.57 eV, in Gallium Nitride (which happens to be detrimental for certain transistors) by using Scanning Probe - Deep Level Transient Spectroscopy (SP-DLTS) to probe its spatial distribution. For the first time, this trap species is mapped with high spatial resolution and it is found to exhibit strong spatial localization in the form of "trap clusters". Through a correlative study with Electron Channeling Contrast Imaging (ECCI), this trap is found to be located at pure edge dislocations. In another study, the impact of iron on the spatial distribution of this trap is investigated, and it is found that the iron causes a more spatially-uniform trap distribution. One possible explanation is that the EC - 0.57 eV traps are directly related to iron atoms that are gettered by edge dislocations in Gallium Nitride. To better understand how the SP-DLTS maps relate to the trap concentration, simulations are performed. A comparison between the measurement and simulation shows reasonable agreement for the two GaN samples studied here. In collaboration with fellow graduate student Darryl Gleason, a study is conducted on a different device geometry (AlGaN/GaN heterostructures with semi-insulating GaN layers). This study allows for the characterization of two trap species in the GaN layer (one of which is the EC - 0.57 eV trap), and good agreement is found between macroscopic DLTS and SP-DLTS for both trap species. Finally, the first Ballistic Electron Emission Microscopy (BEEM) measurements on Ga2O3 are presented, through which the spatial homogeneity of two types of Schottky diodes (Pt/Ga2O3 and Au/Ga2O3) are investigated. In the case of Pt, the Schottky Barrier Height (SBH) is found to be effectively spatially uniform, but it shows evidence of time-dependence. In the case of Au, two samples were investigated, one of which showed well-defined "low-SBH patches" although the majority of the sample appeared to be spatially uniform, while the other Au sample did not show low-SBH patches in the areas investigated thereby indicating a much more homogeneous surface. These investigations can serve as the baseline for future SP-DLTS and BEEM studies of GaN and Ga2O3 as well other semiconductor systems.
Jonathan Pelz (Advisor)
Steven Ringel (Advisor)
Nandini Trivedi (Committee Member)
Yuri Kovchegov (Committee Member)
293 p.
Physics
Scanning Probe Microscopy; Deep Level Transient Spectroscopy; SP-DLTS; Scanning Tunneling Microscopy; Ballistic Electron Emission Microscopy; Semiconductors; Materials Characterization; Finite Element Analysis; COMSOL Multiphysics Simulations

Recommended Citations

Citations

  • Galiano, K. (2020). Scanning Probe Microscopy Measurements and Simulations of Traps and Schottky Barrier Heights of Gallium Nitride and Gallium Oxide [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1576715425331868

    APA Style (7th edition)

  • Galiano, Kevin. Scanning Probe Microscopy Measurements and Simulations of Traps and Schottky Barrier Heights of Gallium Nitride and Gallium Oxide. 2020. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1576715425331868.

    MLA Style (8th edition)

  • Galiano, Kevin. "Scanning Probe Microscopy Measurements and Simulations of Traps and Schottky Barrier Heights of Gallium Nitride and Gallium Oxide." Doctoral dissertation, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1576715425331868

    Chicago Manual of Style (17th edition)

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