III-V nanowires studied using cathodo-luminescence
Event details
| Date | 22.05.2012 |
| Hour | 09:30 |
| Speaker | Anders Gustafsson, Lund University, Sweden |
| Location |
DIA003
|
| Category | Conferences - Seminars |
We investigated properties of GaAs- and InP-based nanowires (NWs) on a sub-micron scale using cathodo-luminescence imaging and spectroscopy. All NWs were grown by MOCVD, seeded by size-selected gold particles. The diameter of the gold particles in this study was typically 30 - 80 nm. The composition in the core was either kept constant (e.g. GaAs or InP) or changed along the length (e.g. a segment of GaInAs in a GaAs core). The emission from the core depends strongly on growth temperature, surface preparation and crystal structure of the GaAs. Axial GaAs/GaInAs/GaAs heterostructures were used to study diffusion effects and radial hetero-structures were studied with respect to homogeneity. Uncapped GaAs NWs show a diffusion length of about 100nm. When capped with an AlGaAs, it improves to about 1µm. The InP cores were covered by thick InP, followed by a thin InAs and a thick InP layer. The InAs layer serves as a radial quantum well (RQW). In addition, the crystal structure of the InP core can result in a controlled super-lattice of segments of zinc-blende (ZB) and wurtzite (WZ), with typical segment lengths of about 200nm. The RQW shows thickness fluctuations differing by a single InAs layer in thickness on the pure WZ. Growth on the super-lattice results in larger thickness variations, forming quantum dots on the ZB facets. The shell can improve the emission intensity, as long as it is defect free, which is normally the case for AlGaAs on GaAs. However when the shell is strained, like GaInP on GaAs, dislocations can be introduced into the shell. For low mismatch this can lead to local relaxation of the strain, as evidenced by local variations in the emission energy from the NW cores. For a higher mismatch, the emission can be degraded locally due to the introduction of dislocation, resulting in dark bands in the images of the NW cores.
Practical information
- General public
- Free
Organizer
- Fontcuberta i Morral Anna <[email protected]>
Contact
- Fontcuberta i Morral Anna <[email protected]>