Project Description: A broad-based interdisciplinary program is proposed to develop and characterize new tetrahedral semiconductor systems consisting of alloys of group-IV and III-V compounds that are inaccessible using traditional methods. The program is based on a recent breakthrough at Arizona State University, where the principal investigators, under support from a Focused Research Group program from the Division of Materials Research at NSF, discovered an entirely new way to combine Al, P, As, and N with Si to synthesize epitaxial films devoid of the phase segregation issues that until now prevented the development of (III-V)IV alloys for applications in optoelectronics. The ASU approach is based on the use of purposely-assembled molecular precursors that incorporate fully pre-formed units in which the III, V, and IV elements are bonded as desired in the solid state. The roadmap of the project includes the study of the atomic level structure and possible ordering effects in the alloys, the systematic investigation of their optical properties, the optimization of the growth protocols and resulting materials properties en route to photovoltaic devices, and the generalization of the synthesis approach to include Ge another III-V elements, as well as alternative nanosynthesis approaches that may lead to additional (III-V)IV systems on silicon, germanium and other industrially relevant platforms. Intellectual Merit: In earlier approaches to the growth of (III-V)IV alloys, the column-III, -IV, and -V components were separately delivered and allowed to react at high temperatures. This led to unacceptable phase separation issues and also prevented control of the structure-composition relationship. The new method developed at ASU is based on molecular precursors that in principle can deliver entire tetrahedral units containing three group-IV atoms and a single III-V pair intact into the growing structure. These features not only prevent phase separation, but make it possible to synthesize films with exceptional structural properties hitherto impossible to attain in the (III-V)-IV composition class. In addition to the AlPSi3, (AlP)xSi5-2x, AlAsSi3, Al(As1-xPx)Si3, Al(P1-xNx)Si3, and Al(As1-xNx)Si3 already demonstrated, the method will be generalized to include most group IV and III-V elements by taking advantage of the principal investigators expertise in molecular design as well as fabrication of semiconductors on engineered substrates. Broader Impact and Outreach: The ASU materials have already attracted attention as potential candidates for multijunction solar cells on Si. The project will not only advance the materials science of these materials to the point where photovoltaic devices can begin to be explored, but will seek to expand applications in this area by introducing new compounds within the same class of materials which display widely tunable band gaps for high efficiency photovoltaics. The project will combine the expertise of investigators with backgrounds in chemistry, materials science, and physics for a systematic program leading to the exploration of the synthesis and properties of these new materials. The outreach and education component of the program will include the development of multidisciplinary courses, workshops and web-based educational resources. The course content will combine synthesis, characterization, and theory/simulation components covering both molecular and solid state topics. Annual workshops will also be organized to showcase the ASU nanosynthesis-based approach to materials development. These workshops will include participants from minority organizations and institutions, as well as experts from industry and national laboratories.
|Effective start/end date||9/1/13 → 8/31/17|
- National Science Foundation (NSF): $788,057.00