Dimitris N. Chorafas Foundation Award 2018: Heidi Potts

Gold-free Growth of InAs Nanowires Growth, Structural & Electrical Properties
EPFL thesis n°7939 (2017)
Thesis director: Prof. A. Fontcuberta i Morral

“For her pioneering contributions in the field of synthesis of nanoscale semiconductors. Her discoveries include the engineering of shape and crystal purity of indium arsenide nanowires through basic elucidation of self-assembly processes. This work opens new perspectives in next generation quantum computing devices based on Majorana Fermions”

Semiconducting nanowires are promising building blocks for next generation electronic and optoelectronic devices, and they are unique structures to study fundamental physical effects. Among different semiconductors, InAs is particularly interesting for electronic applications and quantum transport. In order to use InAs nanowires, several challenges have to be addressed, including their growth, their crystal structure, their surface properties, and the ability to fabricating single-crystalline networks. In this thesis InAs and InAsSb nanowires were grown in a bottom-up approach by molecular beam epitaxy. We demonstrated how to achieve control of the growth direction in order to have vertical nanowires and we showed that the direction can be changed during the growth, resulting in nanowire junctions. This constitutes the first step to obtain nanowire networks which are of great interest for applications including quantum computation. We also showed that crystal structural defects can be suppressed by adding antimony (Sb), which is relevant in order to control the properties of a nanowire. Finally, we studied the electrical properties of our nanowires, in particular focusing on surface passivation.