MIOMD-XI Speakers    
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1.  Prof. Shanthi Iyer, North Carolina A&T State University, USA
Late-Breaking Results: Heteroepitaxial Growth of Dilute InSbN on GaAs by Molecular Beam Epitaxy for Long Wavelength Infrared Applications
Speaker Biography: Dr. Shanthi Iyer completed her doctorate in physics at the Indian Institute of Technology, Delhi, India in 1983. Her dissertation work was focused on transparent and conducting oxides by spray pyrolysis and transparent conducting oxide/Si solar cells. She joined the faculty rank in the Department of Electrical and Computer Engineering at North Carolina A&T State University in 1981 and since then has been working on compound semiconductors. Currently she holds a joint faculty appointment with Joint School of Nanoscience and Nanoengineering at Greensboro. Prof. Iyer has been responsible for the initiation and development of NCA&TSU’s state of the art Molecular Beam Epitaxy (MBE) Laboratory and associated academic and research programs. Her current research work in the MBE growth, characterization and nanostructured device fabrication is based on novel dilute nitride antimonide narrow band gap compound semiconductors for infrared sources and detectors, encompassing a wide infrared wavelength region from 1 μm to 20 μm. She was also the Director of the Center of Excellence for Battlefield Capability Enhancements at NCA&TSU, which focused on developing technologies for environmentally stable flexible panel displays. The other research projects in progress include transparent amorphous oxide thin film transistors on plastic substrates for flexible electronics.

Summary: The distinguishing feature of dilute nitride III-V semiconductors lies in large simultaneous reduction in the band gap and lattice parameter, when N is incorporated in small amounts in an otherwise wide band gap III-V material system. In particular, N incorporation in InSb is attracting great attention due to potential applications in the long wavelength infrared (LWIR) applications. However, relatively small atomic size of N with respect to Sb makes the growth of good quality InSbN layers challenging with enhanced N concentration. Hence optimization of growth conditions is critical to the growth of high-quality InSbN epilayers for device applications. In this paper, we report on the correlation of structural, vibrational, electrical and optical properties of molecular beam epitaxially (MBE) grown InSbN epilayers grown on GaAs substrates, as a function of varying growth temperatures, annealing and doping. Two dimensional (2D) growth of InSb and InSbN epilayers were confirmed from dynamic reflection high energy electron diffraction (RHEED) patterns. High crystalline quality of the epilayers is attested to by a low full width at half maximum (FWHM) of 200 arcsec from high resolution x-ray diffraction (HRXRD) scans and by the high intensity and well-resolved InSb longitudinal optical (LO) and 2nd order InSb LO mode observed from micro-Raman spectroscopy. The active N incorporation in these InSbN epilayers is estimated to be 1.4 % based on HRXRD simulation. Lower growth temperature of 290 °C was found to be optimum for the formation of more substitutional N (in the form of In-N) and less interstitial N (in the form of Sb-N, N-N and In-N-Sb) in the InSbN epilayers, while higher growth temperature of 380 °C promotes the formation of In-N-Sb bonding. The best room temperature (RT) and 77 K electrical transport parameters and maximum redshift in the absorption edge have been achieved in the InSbN epilayer grown in the 290 °C ~ 330 °C temperature range. Annealing was observed to lead to improved quality of the layers as attested by Raman spectra with reduction in the background carrier concentration from 1018 cm-3 from as-grown to 1016 cm-3 and mobility in 104 cm2/V·s range. However the net N incorporation also reduced during the process and absorption edge shifted from ~9 µm to ~10 µm. Improvement in the quality of the as-grown epilayers with enhanced N incorporation in lightly p-doped layers will also be presented in this work.
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