Atomic Modeling and Controlled Formation of III-V Nanopillars by Catalyst-Free Growth Mode

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Technical: This project seeks fundamental understanding of surface kinetics and crystal formation with respect to patterned nanopillar MOCVD epitaxy. Specific goals are to establish a physical model to predict preferential adatom incorporation on III-V semiconductor nanopillars, and to experimentally verify and optimize the formation and characteristics of the nanopillar structures. The project has three primary components: 1) experiment verifiable predictive physical modeling of 3D surface dynamics, 2) correlated nanopillar characterizations and analytical simulations, and 3) controlled preferential nanopillar epitaxy on predetermined sites. Unlike semiconductor nanowires grown using catalytic metal nanoparticles (e.g., Au), these nanopillars are grown without catalysts on masked substrates with lithographically defined nanopatterns. This approach obviates metallic contamination and provides nanopillar placement, along with subsequent device mask registration. Simulation of atomic surface dynamics, based on ab-initio density functional theory, Wulff's theory and integrated with elastic strain and thermal kinetics components, will be conducted to relate preferential adatom incorporation to nanopillar faceting, surface energy, and growth parameters. Correlated measurements of structural, compositional, electrical, and optical properties will be performed, and combined with mathematical simulation for extraction of nanopillar properties including surface state density, carrier dynamics, and quantum effects. Non-technical: The project addresses basic research issues in a topical area of materials science with technological relevance in electronics and photonics. The materials and nanostructures being studied can potentially serve as basic building blocks for advanced optoelectronic devices. The project emphasizes integrated education and research in training of pre-college, undergraduate, and graduate students through laboratory participation, complementary coursework development, and scientifically focused community K-12 involvement. Both PIs are strongly committed to inclusion and broadening participation of under-represented minority groups in undergraduate and graduate research. Support for undergraduate laboratory employment is budgeted and a plan is in place for focused recruiting through student URM (underrepresented minorities) societies and historically URM colleges, as well through the UCLA Center for Engineering Excellence and Diversity (CEED). Technology transfer is included through collaboration with several companies and national laboratories.