Loading...
Direct growth of III-V solar cells on V-groove Si substrates
Saenz, Theresa E.
Saenz, Theresa E.
Citations
Altmetric:
Advisor
Editor
Date
Date Issued
2023
Date Submitted
Keywords
Collections
Research Projects
Organizational Units
Journal Issue
Embargo Expires
2025-01-29
Abstract
The direct growth of III-V semiconductors is interesting for a number of optoelectronic applications, including high-efficiency multijunction solar cells and on-chip lasers. Here, I report on the development of GaAs solar cells grown by metalorganic vapor phase epitaxy (MOVPE) on nanopatterned V-groove Si substrates. V-groove nanopatterns are beneficial for both material quality and cost reasons. Their (111) surface faceting prevents the formation of antiphase boundaries typically problematic in III-V-on-Si heteroepitaxy, and they can be fabricated on wafers polished by low-cost wet etching methods as opposed to typical epi-ready wafers. If good material quality can be achieved, multijunction solar cells with a conversion efficiency upwards of 30% are possible.
This thesis focuses on efforts to grow low-defect-density GaAs on V-groove Si templates by MOVPE with the goal of producing a high-efficiency GaAs solar cell. Studies on the nucleation of near-lattice-matched GaP on the V-groove templates and the coalescence process resulted in a coalesced GaP thin film with a root-mean-square roughness of 0.2 nm and a threading dislocation density of 5\times10^7 cm^{-2}. High-quality GaAs was then grown on the coalesced GaP layer, requiring the implementation of dislocation reduction strategies to produce a film with a defect density suitable for solar cell growth. In this work, thermal cycling annealing and a step-graded dislocation filter are used to produce a threading dislocation density of 3\times10^6 cm^{-2}$in GaAs on V-groove Si. GaAs solar cells grown on this low-defect template with also be discussed, with a focus on efforts to control the formation of thermal-expansion-induced misfit dislocations found at active interfaces in the solar cells, as well as controlling cracking in the III-V layers.
Associated Publications
Rights
Copyright of the original work is retained by the author.