A Study of GaAsSb Nanowires by Molecular Beam Epitaxy for Near IR Applications
Final rept. 15 Jun 2011-14 Jun 2015
NORTH CAROLINA AGRICULTURAL AND TECHNICAL STATE UNIV GREENSBORO
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Ga assisted growth of axial and core-shell configured GaAsGaAsSbGaAs heterostructured nanowires containing different Sb compositions by molecular beam epitaxy are reported. Substrate preparation prior to the growth was found to be critical for achieving all vertical NWs with high nanowire NW density in the 8x108cm2 range. The morphological, structural and optical properties of these NWs were correlated using low temperature photoluminescence PL, Raman spectroscopy, transmission and scanning electron microscopies and X-ray diffraction. Red shift up to 0.9 eV in the 4K photoluminescence PL spectra is obtained with increasing Sb incorporation in core-shell configured nanowires. Though a maximum shift up to only 1.1 eV was achieved in the axial configuration, it was largely free of planar defects. First reports of bandgap tuning up to 1.3 m in GaAsGaAsSbGaAs based core-shell nanowires by incorporation of dilute amount of N are also presented. The observation of room temperature PL emission on as-grown nanowires demonstrates the advantage that the dilute nitride system offers in the NW configuration. Be doping of the GaAs NW ensemble was examined to realize an axial p-i-n heterostructured NW photodetector. NW aspect ratio, growth rate, NW density and doping efficiency were found to be strongly influenced by group VIII ratio, Be effusion cell temperature and the coreshell configuration.