Few-electron quantum dots in nanowires

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 ∼50 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.