We demonstrate storage of electrons in semiconductor nanowires epitaxially grown from Au nanoparticles. The nanowires contain multiple tunnel junctions (MTJs) of InP barriers and InAs quantum dots designed such that the metal seed particles act as storage nodes. By positioning a second nanowire close to the seed particle it is possible to detect tunneling of individual electrons through the MTJ at 4.2 K. A strong memory effect is observed in the detector current when sweeping the writing voltage.

We demonstrate transport spectroscopy on bottom-up grown few-electron quantum dots in semiconductor nanowires. The dots are defined by InP double barrier heterostructures in InAs nanowires catalytically grown from nanoparticles. By changing the dot size, we can design devices ranging from single-electron transistors to few-electron quantum dots. In the latter case, electrons can be added one by one to the dots from 0 to similar to50 electrons while maintaining an almost constant charging energy, with addition spectra of the devices displaying shell structures as a result of spin and orbital degeneracies. The reduced dimensionality of the nanowire emitter gives rise to pronounced resonant tunneling peaks, where a gate can be used to control the peak positions.

We present growth studies of InAs nanowires nucleated from lithographically positioned Au seeds on InAs (111)B substrates. The nanowires are grown in a chemical beam epitaxy system and exhibit high aspect ratios and high homogeneity in length and width. Investigations of wire growth rate as a function of diameter, density, and time were performed and the results indicate that 80% of the growth is due to In species diffusing from the (111)B substrate surface. Furthermore, we have established that the diffusion length on the {110} wire side surfaces exceeds 10 mum. We also observe a decreasing length growth rate with increasing wire diameter.