Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List

Full text release has been delayed at the author's request until December 15, 2025

ETD Abstract Container

Abstract Header

Embedded HSQ Nanostructures in GaAs Homoepitaxy by MOCVD and MBE: A Study of Selective Area Epitaxy at the Nanoscale

Price, Aimee Lynn Bross
http://orcid.org/0009-0004-8148-5050
http://rave.ohiolink.edu/etdc/view?acc_num=osu1732536772467339

Abstract Details

2024, Master of Science, Ohio State University, Electrical and Computer Engineering.
Selective area epitaxy in III-V compound semiconductors has been used for decades in applications such as patterned quantum dots, strain blocking in metamorphic growth, and substrate removal. Recent work in integrated photonic structures, photonic crystal lasers, and metamaterials have led to a renewed interest in patterned and selective epitaxy. The ability to embed dielectric materials into an epitaxial layer or to create regions of complete selectivity (no growth) allow for flexibility in device design and monolithic integration. Advances in lithography and fabrication techniques offer opportunities to explore selective epitaxy and length scales that were not previously accessible. This work focuses on nanoscale selective epitaxy using hydrogen silsesquioxane (HSQ) as the dielectric mask. HSQ becomes a silicon oxide, nearly identical to SiO2, after electron beam exposure and development. HSQ patterns smaller than 20 nm wide, 90 nm tall on a 10 um grid on GaAs (100) offcut 6° toward the nearest (111)A were used in selective epitaxy by both molecular beam epitaxy (MBE) and organometallic chemical vapor deposition (MOCVD). Addionally, on-axis GaAs (100) substrates were used in MOCVD as a comparison to the 6° offcut. The grid lines were aligned to the [011] and [01¯1]. The goal of this work was to understand the interaction between the HSQ “nanowalls” and the epitaxy. The specific orientation of HSQ nanowalls had the most significant impact on local epilayer morphology for both MBE and MOCVD growths. Interestingly, the two growth methods yielded effectively opposite effects, with vast differences in epitaxial wetting, growth initiation/inhibition, lateral overgrowth, and type/number/propagation/direction of material imperfections. For both on-axis and off-cut substrates, the MOCVD growths possess highly faceted trenches along the [011] direction that effectively extend down to the substrate surface; no GaAs growth is observed over or adjacent to the HSQ lines. In the orthogonal direction, along the [01 ̅1 ], the growth yielded shallow, smooth trenches above the HSQ for 6 degree off-cut substrates and smooth overgrowth for on-axis. The initial indication is that MOCVD-grown GaAs does not wet the [011]-oriented HSQ lines, with resultant growth on [111] planes preventing coalescence. However, the [01 ̅1 ]-oriented lines were embedded into the GaAs. The impact was different for the growth in the [011] from the HSQ nanowalls and the opposite [0 ¯1¯1], with faceted growth at 15° in the former and shallow growth in the latter. We present a step flow based mechanism explaining this result. In the MBE grown material at 610°C, the result is heavy, jagged faceting above the [01¯1] oriented HSQ, with the orthogonal yielding full overgrowth with no observable faceting or growth inhibition. The striking differences between the MBE and MOCVD epilayers highlight the differences in the growth techniques themselves and the interaction with foreign materials, including the role of directional surface diffusion and reactive surface chemistry.
Tyler Grassman, Ph. D. (Advisor)
Steven Ringel, Ph. D. (Committee Co-Chair)
93 p.
Electrical Engineering; Materials Science
Epitaxy; Selective Epitaxy; Electron Beam Lithography; MOCVD; MBE; GaAs

Recommended Citations

Citations

  • Price, A. L. B. (2024). Embedded HSQ Nanostructures in GaAs Homoepitaxy by MOCVD and MBE: A Study of Selective Area Epitaxy at the Nanoscale [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1732536772467339

    APA Style (7th edition)

  • Price, Aimee. Embedded HSQ Nanostructures in GaAs Homoepitaxy by MOCVD and MBE: A Study of Selective Area Epitaxy at the Nanoscale . 2024. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1732536772467339.

    MLA Style (8th edition)

  • Price, Aimee. "Embedded HSQ Nanostructures in GaAs Homoepitaxy by MOCVD and MBE: A Study of Selective Area Epitaxy at the Nanoscale ." Master's thesis, Ohio State University, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=osu1732536772467339

    Chicago Manual of Style (17th edition)

osu1732536772467339
© 2024, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.