GaN and GaAs nanowires

Semiconductor Nanowires (NWs) are structures with an extremely high aspect ratio and a diameter less than 100 nm that are created in a bottom-up approach. Feature sizes of less than 10 nm can be achieved without any lithography in an abundance of material systems. Therefore, NWs have the potential for ground-breaking applications in electronics and optoelectronics. In addition, the small size and the high surface-to-volume ratio make NWs an interesting subject for fundamental studies.

In many cases, growth starts from droplets of a catalyst, typically gold, whose size defines the diameter of the NWs. This approach is called the vapor-liquid-solid mechanism (VLS). As an alternative, NW formation may in certain cases take place without any catalyst, i.e. self-induced. Due to the small diameter of NWs, strain can be reduced in radial direction. Thus, lattice mismatch is less critical than for planar growth, and new material combinations are possible in heterostructures. Moreover, epitaxial growth of various semiconductors on silicon substrates is feasible. This opens up the way to combining the advantages of other semiconductors, e.g. in terms of light emission or mobility, with the maturity of silicon technology.

We study the growth of both group III-arsenide and nitride NWs.