ABSTRACT
Associating different semiconductor materials in a single crystalline
nanowire (NW) opens a rich field of investigations and applications.
In this respect, the one-dimensional (1D) geometry of NWs offers
several advantages over planar structures. The range of possible
heterostructure geometries is much larger. We briefly review how
each type of heterostructure may be fabricated. Moreover, it is often
necessary to assemble materials with different lattice parameters.
The sidewalls of the NWs are free surfaces that allow a very efficient
elastic relaxation of the misfit strain. This allows for a much larger
range of defect-free structures than in planar heterostructures or
even in quantum dots (QDs). In axial heterostructures, this deeply
modifies the competition between elastic and plastic relaxation.
Calculations of elastic and plastic strain relaxation show that
the critical layer thickness beyond which dislocations appear is
much higher than in planar structures for NWs of standard radii.
There also exists a critical NW radius below which an arbitrarily
thick misfitting layer can be grown. In core-shell heterostructures,
the sidewalls also allow for an efficient strain relaxation, and
appropriate critical dimensions (shell thickness and core radius) can
be calculated. Finally, strain can be used to engineer the physical
properties of heterostructres in order to obtain certain electronic or
optical properties.
