GLAM Special Seminar
Geballe Laboratory for Advanced Materials
Friday, 15 September 2017 at 10 a.m.
Location: McCullough, room #335
Host: Paul McIntyre
Georgia Institute of Technology, School of Chemical & Biomolecular Engineering
The growth and optical properties of III-V nanostructures grown by molecular beam epitaxy
In this talk, the growth and characterization of the optoelectronic properties of III-V semiconductor nanostructures namely nanowires and nanoscale membranes will be investigated. III-V semiconductors possess promising intrinsic properties like direct band gap, high electron/hole mobility and spin-orbit interaction which makes them interesting for a wide range of applications such as high speed electronics, optoelectronics and photovoltaics. Nanostructures enable the exploitation and further functionalization of the inherent semiconductor properties. The nanostructures we study in the scope of this study are grown with molecular beam epitaxy, which enables us to obtain ultra-pure nanostructures with high crystalline quality.
In the first part of this talk we will briefly mention the growth of GaAs nanowires and the applications they are employed in as scanning force microscopy and lasing. The rest of this talk will be dedicated to the growth of defect-free structures. Two methods will be presented to create defect-free pure zinc-blende GaAs nanostructures. The first one is to modify the polarity of GaAs nanowires. We optimize the growth parameters to obtain a high yield of (111)A nanowires on (100) GaAs. GaAs nanowires grown in (111)A direction exhibited a defect-free structure in contrast to the nanowires grown in (111)B direction. Our second approach is to grow elongated nanostructures and control their orientation to ‘lock out’ the defects. When these nanostructures, GaAs nanoscale membranes, are oriented in <11-2> direction on a (111)B GaAs substrate they exhibit pure zinc-blende crystalline structure. Their superior crystalline quality is confirmed with transmission electron microscopy and optical characterization techniques, i.e. photoluminescence and cathodoluminescence. Their growth mechanism and parameter window is investigated in detail. Finally, GaAs nanoscale membranes are used as templates for quantum heterostructures.