SusChEM: Molecular Routes to New Classes of Polar and Non-Polar Alloy Semiconductors

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Technical Description: The project investigates the fabrication and properties of (III-V)-IV alloys based on the recent discovery of a synthesis approach that eliminates phase segregation effects in these alloys. The essential idea is to build the alloy crystal from pre-formed molecular units containing three group-IV atoms and a single III-V pair in tetrahedral geometry. Growth is done using chemical vapor deposition on readily available silicon or germanium substrates. The research includes determination of the atomic level structure of the alloys, systematic study of their optical properties, investigation of compositional and doping control for potential semiconductor applications, and generalization of the approach to include most group III, IV, and V materials. An additional goal is to develop other classes of materials based on the concept of molecular building blocks.Non-technical Description: Modern research in materials science is strongly focused on the design and synthesis of materials not available in nature. The molecular approach to crystal growth exemplified by this project represents a new tool for this quest that may lead to materials with unique properties. In particular, some of the materials to be studied, including alloys of Al, P, N, and Si, are expected to have lattice dimensions similar to a silicon crystal and could form the basis for Si-based tandem solar cells. Single-layer silicon solar cells dominate the current photovoltaics market but their efficiency is limited to about 25%. The cell efficiency could exceed 30% in tandem structures, with large societal impact. The uniqueness of the molecules-to-solids approach also creates opportunities for multidisciplinary education. The project includes the development of new courses that allow students to become familiar with the chemistry and physics concepts needed to pursue materials research. Provisions are also being made to create a database of chemical precursors, to be made available to the community at large, which insures that other researchers have access to the synthetic innovations developed under this project.This project is funded jointly by the Electronic and Photonic Materials (EPM) and Solid State and Materials Chemistry (SSMC) Programs in the Division of Materials Research.