CAREER: Lateral Composition Modulation in InAs/GaSb Superlattices: Nanometer Sized Quantum Wires

University Of Houston, Houston TX

Investigators

Abstract

This CAREER project represents an integrated research, instructional and outreach activity. The aim of the project is to gain fundamental understanding of "natural" quantum wires formed by lateral composition modulation (LCM) during molecular beam epitaxial (MBE) growth of InAs/GaSb superlattices, InxGa1-xSb single layers and InAs/InxGa1-xSb multilayers, where these materials may be utilized for applications such as nano- and opto-electronic devices. This research may significantly impact the development of solid-state technologies utilizing InAs/(In)GaSb LCM materials forming the basis for new LCM devices, such as lasers based on quantum wire (QWR) technology. An objective of the research plan is to control the formation of the LCM nanostructures, i.e., degree of modulation and modulation wavelength, and address re-producibility issues. This will be done through analysis using migration-enhanced epitaxy (MEE) to effectively control interfacial composition since LCM is associated with a surface undulation at the interface. Another objective is to structurally characterize the modulated structures by conventional and advanced x-ray diffraction techniques, i.e., in plane x-ray diffraction (XRD), grazing-incidence diffraction (GID) and grazing-incidence small-angle scattering (GISAXS). These techniques will allow probing of the LCM structures in terms of depth/interface analysis, not available through conventional XRD. Cross sectional transmission electron microscopy (XTEM) will also be used in conjunction with XRD to yield a survey of the physical structure of the LCM. A third objective is to characterize the optical and electrical behavior of these structures by polarization dependent photoluminescence and magneto-photoluminescence to demonstrate quantum wire behavior, and Hall effect measurements to determine the materials prospect for future nano- and opto-electronic device development. An established collaboration with the Naval Re-search Laboratory (NRL) on the growth of these materials will greatly enhance the success of the project and broaden and enrich the perspectives of students involved in the project beyond the confines of the PI's laboratory through summer internships. %%% The project addresses fundamental materials science research issues having technological relevance. An important feature of the project is the strong emphasis on education, and the integration of research and education. The educational plan extends beyond usual graduate and under-graduate student activities via four avenues: (1) Development of a course based on experimental techniques in solid-state physics and its role in the future of nanotechnology targeted toward first and second year physics and engineering graduate students. This course will introduce experimental techniques of solid-state physics as they apply to nanotechnology as well as include laboratory visits and experimental demonstrations; (2) Advising undergraduate, graduate and post-doctoral associates in the PI's laboratory will broaden their individual perspectives beyond that of a single specialty. These students will also assist with laboratory demonstrations for an experimental solid-state physics course being developed; (3) Mentoring and exposing undergraduate students involved in the Louis Stokes Minority Alliance Program (LSAMP), to solid-state nanotechnology through laboratory positions and laboratory tours as well as presenting lectures at the LSAMP annual conference and (4) Yearly lectures at local high schools on the impact of nanotechnology on society. ***