Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 26: Quantum Wires: Transport Properties (organized by HL)

TT 26.3: Talk

Monday, March 31, 2014, 16:30–16:45, POT 006

Ga droplet templates: Density control of self-assisted GaAs nanowires — •Hanno Küpers, Faebian Bastiman, Claudio Somaschini, and Lutz Geelhaar — Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin

The self-assisted growth of GaAs nanowires (NWs) on Si is a popular approach for integrating III-V materials on Si. However, growth on unpatterned Si substrates suffers from a lack of control over nanowire density and a high degree of parasitic growth. We report on a new two-step NW density control technique for self-assisted GaAs nanowires grown on Si(111) by molecular beam epitaxy. The first step involves pre-depositing Ga on the substrate utilising a relatively high Ga flux at elevated temperatures. The Ga droplet density can be controlled by changing the magnitude of the Ga flux and the duration of the Ga pre-deposition time. The resulting Ga droplet template provides selective density control for ensuing NW growth. In this second step a maximum of 50% of the Ga droplets can be successfully converted into vertical NWs. The magnitude of the As flux and the size distribution of the Ga droplets underpins both the observed NW yield and the type of parasitic growth. A 10% improvement in the vertical yield can be gained by including a droplet ripening step before As flux exposure in order to narrow the droplet size distribution, but the Gaussian nature of the distribution prevents access to a 100% vertical yield.