Olubukola Ayanbajo – Seminar/MS Thesis Defense – Wednesday, March 21, 2018 at 2:30 P.M.
JSNN – Olubukola Ayanbajo- MS Thesis Defense/Wednesday Seminar
Candidate: Olubukola Ayanbajo
Major Advisor: Shanthi Iyer, Ph.D.
Time: 2:30 P.M. – 4:00 P.M.
Location: JSNN Room 209 Open Area2907 E. Gate City Blvd., Greensboro, NC 27401
Title: “Micro-photoluminescence Study of Bandgap Engineered GaAsSb Nanowires Grown by Molecular Beam Epitaxy.”
The advancement in nanotechnology, along with the growing need for smaller, faster and efficient electronic and optoelectronic devices, has made III-V nanowires (NWs) the focus of many researchers. Their potential for improved performance in optoelectronic devices and optical telecommunication applications and heterogeneous integration to silicon platform due to the ability to implement the NWs in different architectures, as well as their tunable bandgap, high intrinsic mobility, and strain tolerance, makes them very attractive for next-generation devices. In this thesis, μ-photoluminescence (PL) spectroscopy has been used to extract variety of information on the GaAsSb NWs grown using Ga-catalyzed molecular beam epitaxy (MBE). The low-temperature PL spectra of bandgap engineered axial GaAsSb NWs showed the expected redshift, as the Sb concentration in NWs was increased from 20 at. % to 85 at. %. Effect of the two-step temperature growth pathway for higher incorporation of Sb at. % was investigated using both room temperature and 4K PL measurements. 4K PL emission of up to ~1.7 μm was observed for axial GaAs0.2Sb0.8 NWs. The behavior of laser excitation dependent PL curves suggests band-to-band optical transitions to be of type-I nature. Effect of beryllium incorporation in GaAsSb/AlGaAs NWs was investigated. The increased PL intensity in a doped double shell configuration was observed attributed to the surface passivation. Doped GaAsSb/AlGaAs showed significant bandgap narrowing at Sb 18 at. % composition. Finally, single nanowire PL measurement confirmed the high quality of GaAsSb NWs grown on graphene.