dc.contributor.author	Jain, Nikhil	en
dc.contributor.committeechair	Hudait, Mantu K.	en
dc.contributor.committeemember	Lester, Luke F.	en
dc.contributor.committeemember	Heremans, Jean J.	en
dc.contributor.committeemember	Plassmann, Paul E.	en
dc.contributor.committeemember	Orlowski, Mariusz Kriysztof	en
dc.contributor.department	Electrical and Computer Engineering	en
dc.date.accessioned	2015-05-08T08:01:39Z	en
dc.date.available	2015-05-08T08:01:39Z	en
dc.date.issued	2015-05-07	en
dc.description.abstract	Achieving high efficiency solar cells and concurrently driving down the cell cost has been among the key objectives for photovoltaic researchers to attain a lower levelized cost of energy (LCOE). While the performance of silicon (Si) based solar cells have almost saturated at an efficiency of ~25%, III-V compound semiconductor based solar cells have steadily shown performance improvement at approximately 1% (absolute) increase per year, with a recent record efficiency of 46%. However, the expensive cost has made it challenging for the high efficiency III-V solar cells to compete with the mainstream Si technology. Novel approaches to lower down the cost per watt for III-V solar cells will position them to be among the key contenders in the renewable energy sector. Integration of such high-efficiency III-V multijunction solar cells on significantly cheaper and large area Si substrate has the potential to address the future LCOE roadmaps by unifying the high-efficiency merits of III-V materials with low-cost and abundance of Si. However, the 4% lattice mismatch, thermal mismatch polar-on-nonpolar epitaxy makes the direct growth of GaAs on Si challenging, rendering the metamorphic cell sensitive to dislocations. The focus of this dissertation is to systematically investigate heterogeneously integrated III-V multijunction solar cells on Si substrate. Utilizing a combination of comprehensive solar cell modeling and experimental techniques, we seek to better understand the material properties and correlate them to improve the device performance, with simulation providing a very valuable feedback loop. Key technical design considerations and optimal performance projections are discussed for integrating metamorphic III-V multijunction solar cells on Si substrates for 1-sun and concentrated photovoltaics. Key factors limiting the “GaAs-on-Si” cell performance are identified, and novel approaches focused on minimizing threading dislocation density are discussed. Finally, we discuss a novel epitaxial growth path utilizing high-quality and thin epitaxial Ge layers directly grown on Si substrate to create virtual “Ge-on-Si” substrate for III-V-on-Si multijunction photovoltaics. With the plummeting price of Si solar cells accompanied with the tremendous headroom available for improving the III-V solar cell efficiencies, the future prospects for successful integration of III-V solar cell technology with Si substrate looks very promising to unlock an era of next generation of high-efficiency and low-cost photovoltaics.	en
dc.description.degree	Ph. D.	en
dc.format.medium	ETD	en
dc.identifier.other	vt_gsexam:5046	en
dc.identifier.uri	http://hdl.handle.net/10919/52045	en
dc.publisher	Virginia Tech	en
dc.rights	In Copyright	en
dc.rights.uri	http://rightsstatements.org/vocab/InC/1.0/	en
dc.subject	III–V-on-Si solar cells	en
dc.subject	multijunction solar cells	en
dc.subject	heterogeneous integration	en
dc.subject	solar cell modeling	en
dc.subject	GaAs-on-Si epitaxy	en
dc.subject	Ge-on-Si epitaxy	en
dc.title	Heterogeneous Integration of III-V Multijunction Solar Cells on Si Substrate: Cell Design and Modeling, Epitaxial Growth and Fabrication	en
dc.type	Dissertation	en
thesis.degree.discipline	Electrical Engineering	en
thesis.degree.grantor	Virginia Polytechnic Institute and State University	en
thesis.degree.level	doctoral	en
thesis.degree.name	Ph. D.	en

Heterogeneous Integration of III-V Multijunction Solar Cells on Si Substrate: Cell Design and Modeling, Epitaxial Growth and Fabrication

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