Development of graphene growth surfaces for III-V semiconductors

Modern electronic and optoelectronic device industry is shifting from conventional rigid and bulky devices to smarter, flexible, transparent, economical, extra efficient and multifunctional devices. III-V semiconductor materials are an integral part of these devices due to their superior optical properties and electron mobilities as compared to silicon. However, the use of III-V semiconductor materials is currently reserved for high specification use cases. Two key challenges, which limit their application to emerging technology products are cost and integration. One approach to minimise the cost is to adopt thin films of these materials which can be released from its substrate and heterointegrated with silicon or transferred to flexible substrates. This is of particular interest for energy conversion devices. However, the fabrication of high quality large area thin films at lower cost is still a significant challenge. This work focuses on the development of the emerging technique of remote epitaxy, which exploits an atomically thin two-dimensional (2D) material as an interface layer between a III-V growth substrate and an epitaxial film. For example, 2D material such as graphene coated on GaAs substrates allows the registry information of the underlying substrate to permeate through the graphene and facilitate the formation of exact copy of single crystal growth template. Therefore, the grown layer would replicate the crystal orientation of the underlying substrate. The critical advantage of this technique is that the film is only bonded to the graphene with a Van der Waal’s bond, allowing it to be readily released from the growth substrate non-destructively and subsequently bonded to an alternative flexible substrate to fabricate optoelectronic devices. In this work, we fabricate GaAs thin films epitaxially on graphene coated substrates. I have shown that the CVD graphene grown on Cu, wet transferred to a GaAs substrate can be used as an interface layer for the growth of single crystal epitaxial GaAs films and subsequent exfoliation. We observe wet transfer of graphene leads to the formation of a native oxide layer at the graphene/substrate thus widening the gap between graphene and the substrate. This hinders the remote interaction from the substrate. To mitigate the problem of oxide layer formation we exposed graphene to an Ar-ion beam to create pinhole defects. This allows the desorption of native oxides at elevated temperature and the nucleation of GaAs at defect sites followed by lateral overgrowth. The epilayer is exfoliated from the growth substrate revealing the nucleation of the epilayer through pinholes. We also explore the possibility of semi-dry transferred CVD graphene to avoid native oxide growth at the graphene interface, reducing the need for defect seeding of the epitaxial layer. The processes demonstrated in this work would significantly reduce the cost of fabricating thin films and pave the way for their industrial scale adoption.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Zulqurnain, Muhammad

Advisor dc:contributor.advisor

• Ritchie, David

• Remote Epitaxy
• Graphene
• Molecular beam epitaxy
• Thin films

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/6444f304-53ef-4fe4-b4f3-dced66fadf1f/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

Author Identifier

0000-0002-6612-049X

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/373085