Crystal Structures in GaAs Nanowires: Growth and Characterization
Summary, in English
Metal-organic vapor phase epitaxy (MOVPE) has been used to demonstrate a single temperature approach to achieving high quality WZ-ZB heterostructures. To increase the complexity of the nanowires, heterostructures with controlled ZB inclusions in WZ nanowires were also grown. Detailed post-growth analysis of the seed particle composition suggested a Ga-rich growth environment for WZ, whereas it is possible to grow defect-free ZB in As-rich conditions. To achieve a sharp interface between ZB grown with As-rich conditions and a following WZ segment, the local growth environment has to be returned to Ga-rich before growth is continued. To gain further control of the growth of polytypic GaAs nanowires, the possibility of using HCl as an additive during growth has been explored.
Using in situ transmission electron microscopy, real time growth studies of GaAs WZ-ZB nanowires revealed distinct differences between the two polytypes for the growth dynamics at the seed particle-nanowire interface. By increasing or decreasing the Ga content within the Au-Ga alloy seed particle, crystal structure tuning was achieved, with the wetting angle of the seed particle as the trigger changing between growth of ZB and WZ.
The different atomic arrangements in WZ and ZB GaAs mean that the two polytypes have different electronic, optical and surface properties, even though they have the same composition. This thesis work has determined the nature of the faceting of WZ-ZB heterostructures and the lattice parameters of WZ and the higher order polytype 4H, as well as the band gap of WZ and its and band alignment with ZB.
- Condensed Matter Physics
- Fysicumarkivet A:2015:Jacobsson
- Kimberly Dick Thelander
- Sebastian Lehmann
- Jonas Johansson
- Knut Deppert
- ISBN: 978-91-7623-337-5
- ISBN: 978-91-7623-338-2
29 May 2015
Rydberg Lecture Hall at the Department of Physics, Professorsgatan 1, Lund University Faculty of Engineering, LTH
- Lincoln Lauhon (Prof.)