A superlattice is a nanostructure made of repeating a set of layers of semiconductor materials. Generally, only two materials are involved, although more can certainly be put together to create a superlattice.
Superlattices are generally grown in the crystals' (110) or (001) direction, since these are the easiest structures to actually grow.
There are various ways of creating a superlattice, but currently molecular beam epitaxy is the most common (to my knowledge), as it provides the greatest control over the material composition.
Diagram of a superlattice:
... A | B | A | B | A | ....
... | | | | | ....
... | | | | | ....
... | | | | | ....
Energy diagam (based on the two materials)
________ ________ ________
|___________| |___________| |_______ Conduction Band
___________ ___________ _______
________| |________| |________| Valence band
The superlattice has its own
band properties, such as its own
band gap and its own
dispersion relation. These properties depend upon the two materials of which the superlattice is composed:
Energy diagam (superlattice view)
----------------------------------------------------------Conduction Band
----------------------------------------------------------Valence band