Epitaxial Quantum Wires: Growth, Properties and Applications

Abstract

The opportunity to form one-dimensional (1D) materials and devices via epitaxially nucleated growth of whiskers was realized more than 30 years ago by Wagner and others [1]. At that time, technology as well as the general awareness of the technology on small length-scales only permitted whisker dimensions typically down to the micrometer region. It was first via the pioneering work of Hiruma and coworkers [2] at Hitachi during the early part of the 1990s that the nanometer dimension of nanowires were explored and brought to the level where the potential for nanoelectronic and photonic devices was realized. The approach of Hiruma has during the last few years been developed further by several groups, for instance that led by Peydong Yang at UC Berkeley and the one by Lars Samuelson at Lund University. Besides this special version of nanowire formation via epitaxially nucleated growth, various research groups have been developing the method of spontaneous sprouting of nanowires from catalytic nanoparticles, most noticed being the work by the Lieber group at Harvard University. Much of the present excitement in the field stems from the recent breakthrough in forming nanowires containing ideal heterostructure interfaces [3], hence allowing nanoelectronic [4] and nanophotonic heterostructure devices to be formed. In the following we first describe the background in terms of competitive or alternative methods for realization of one-dimensional semiconductor structures, with an emphasis on comparison between conventional top-down as opposed to self-assembly or bottom-up fabrication methods. We then present some recent progress related to the electronic structure of nanowires, including predictions of phenomena that should be feasible using existing technology. This is followed by a rather detailed description of state-of-the-art fabrication of homogeneous nanowires as well as those containing heterostructures along the one-dimensional axis of the wire. Finally we describe some of the technology required for the creation of electrically contacted nanowires with an emphasis on contact technologies and experimental results for simple and more complex 1D heterostructure devices. An outlook on which direction this technology might take then follows and we will give examples of future challenges and opportunities.