title: Molecular-based synthetic approach to new group IV materials for high-efficiency, low-cost solar cells and Si-based optoelectronics.
abstract: Ge(1-x-y)Si(x)Sn(y) alloys have emerged as a new class of highly versatile IR semiconductors offering the potential for independent variation of band structure and lattice dimension, making them the first practical group IV ternary system fully compatible with Si CMOS processing. In this paper we develop and apply new synthetic protocols based on designer molecular hydrides of Si, Ge, and Sn to demonstrate this concept from a synthesis perspective. Variation of the Si/Sn ratio in the ternary leads to an entirely new family of semiconductors exhibiting tunable direct band gaps (E(o)) ranging from 0.8 to 1.2 eV at a fixed lattice constant identical to that of Ge, as required for the design of high-efficiency multijunction solar cells based on group IV/III-V hybrids. As a proof-of-concept demonstration, we fabricated lattice-matched Si(100)/Ge/SiGeSn/InGaAs architectures on low-cost Si(100) substrates for the first time. These exhibit the required optical, structural, and thermal properties, thus representing a viable starting point en route to a complete four-junction photovoltaic device. In the context of Si-Ge-Sn optoelectronic applications, we show that Ge(1-x-y)Si(x)Sn(y) alloys serve as higher-gap barrier layers for the formation of light emitting structures based on Ge(1-y)Sn(y) quantum wells grown on Si.
authors.affiliation: Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, USA.
authors.forename: Yan-Yan
authors.initials: YY
authors.lastname: Fang
authors.forename: Junqi
authors.initials: J
authors.lastname: Xie
authors.forename: John
authors.initials: J
authors.lastname: Tolle
authors.forename: Radek
authors.initials: R
authors.lastname: Roucka
authors.forename: Vijay R
authors.initials: VR
authors.lastname: D'Costa
authors.forename: Andrew V G
authors.initials: AV
authors.lastname: Chizmeshya
authors.forename: Jose
authors.initials: J
authors.lastname: Menendez
authors.forename: John
authors.initials: J
authors.lastname: Kouvetakis