We report on the site-selective growth of >90% vertical GaAs nanowires (NWs) on Si (111) using self-assisted molecular beam epitaxy. The influences of growth parameters (pre-growth Ga opening time, V/III flux ratio) and processing conditions (reactive ion etching (RIE) and HF etching time) are investigated for different pitch lengths (200-1000 nm) to achieve vertical NWs. The processing variables determine the removal of the native oxide layer and the contact angle of Ga-droplet inside the patterned hole that are critical to the vertical orientation of the NWs. Pre-growth Ga-opening time is found to be a crucial factor determining the size of the droplet in the patterned hole, while the V/III beam equivalent pressure (BEP) ratio influenced the occupancy of the holes due to the axial growth of NWs being group-V limited.
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Deposition-last lithographically defined epitaxial complex oxide devices on Si(100)
The epitaxial growth of SrTiO 3 on Si(100) substrates that have been lithographically patterned to realize deposition-last, lithographically defined oxide devices on Si is explored. In contrast to traditional deposition-last techniques which create a physical hard mask on top of the substrate prior to epitaxial growth, a pseudomask is instead created by texturing the Si substrate surface itself. The Si is textured through a combination of reactive ion etching and wet-etching using a tetramethylammonium hydroxide solution. Desorbing the native SiO x at high temperatures prior to epitaxial growth in ultrahigh vacuum presents no complications as the patterned substrate is comprised entirely of Si. The inverted profile in which the epitaxial oxide device layer is above the textured pseudomask circumvents shadowing during deposition associated with conventional hard masks, thereby opening a pathway for highly scaled devices to be created.
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- PAR ID:
- 10418866
- Date Published:
- Journal Name:
- Journal of Vacuum Science & Technology A
- Volume:
- 40
- Issue:
- 5
- ISSN:
- 0734-2101
- Page Range / eLocation ID:
- 052701
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1116/6.0001939
