Buried Single Crystal Semi-Metal/Semiconductor Nanocomposites for 3D Electronic Materials

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

Nontechnical Description: This project investigates a new class of crystalline metal-semiconductor nanostructure composites. Because of their unique 3-dimensional (3D) nanostructures, these nanocomposite materials have the potential for practical applications for enabling new semiconductor devices, thermoelectrics, photodetectors, and terahertz technologies with broad impacts to society. The mechanism by which these 3D nanostructure composites form is studied by combining atomic-level control of growth with structural and electronic characterization. Changes in growth conditions, such as the proportion of metal to semiconductor components, the growth temperature, substrates with various crystal orientations, and different metal-semiconductor combinations, result in new nanostructures with different properties. The effects of these parameters on growth are modeled and then used to design new materials. This research involves graduate students and postdoctoral associates in interdisciplinary research areas of materials science, electrical engineering, condensed matter and materials physics, and chemistry. In addition, participants of this project are engaged in a variety of educational activities from high-school through graduate level and beyond, which brings people of all ages and under-represented communities into contact with STEM opportunities. Technical Description: The main objective of the project is to establish a fundamental understanding of a surface mediated thermodynamic phase separation mechanism that occurs during the molecular beam epitaxial (MBE) growth of GaSb, GaAs and related compound semiconductors with co-deposition of a rare-earth (RE) element such as Er. The MBE co-deposition results in the formation of embedded epitaxial semi-metallic RE-V rods, branched trees and two-dimensional sheets. Further study includes determining the physical properties of these nanostructures and exploring their potential applications as buried contacts in photodetectors. In-situ atomic level structural, chemical and electronic characterization tools, including scanning tunneling microscopy and spectroscopy plus X-ray photoelectron spectroscopy, are combined with MBE growth to study the growth mechanism at the atomic scale. The electronic and optical properties are studied ex-situ by temperature-dependent magnetotransport, photoluminescence and terahertz (THz) spectroscopy. The fundamental materials exploration of these nanostructured materials could enable future applications as buried contacts for stacked photodetectors and terahertz polarization filters, detectors, and sources.