Formation of Higher Polytypes in III-V - Nanowires

• Applicant: Dr. Jan Schmidtbauer
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: Funded in 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 277838135

Semiconducting nanowires are typically grown with the help of the so-called vapour-liquid-solid mechanism. Nanowire grown from III-V materials often show segments with different crystal structure called polytypes. Polytypism is a known phenomenon and is basically attributed to different stacking sequences of the atomic layers. In III-V nanwires the wurtzite structure (2H) and the zinc blende structure (3C) are the two modifications which are studied most. A general model describing the formation of polytypes during nanowire growth is however, not known up to know. Therefore, the process window for a specific polytype needs to be found starting with theoretical considerations. As a first step, interface energies between droplet and semiconductor need to be calculated in order to study the nucleation of the different crystalline phases. Subsequently it should be confirmed if the resulting influence of growth conditions like supersaturation on the nucleation energy of different polytypes coincide with experimental growth conditions for zinc blende structure and wurtzite structure respectively. The formation of high polytypes should be studied based on these results. Besides the theoretical investigations, nanowire growth experiments by means of metal-organic vapour phase epitaxy are to be conducted in order to find appropriate conditions for the formation of specific polytypes. Process parameters like pressure, temperature, gas flux and partial pressures should be varied. In addition, the use of different metals serving as catalysts is going to be tested in the course of the project.

• DFG Programme: Research Fellowships
• International Connection: Sweden
• Host: Professor Dr. Knut Deppert