This paper reviews the recent progresses obtained by direct growth of III–V semiconductor quantum dots (QDs) on pre-patterned and flat silicon substrates. This combination allows us to study in detail the growth mechanisms of III–V materials on silicon substrates. For the flat surfaces, we concentrate on basic growth studies addressing mainly morphological properties of QD-like structures with a main emphasis on surface preparation and growth parameters. For the pre-patterned substrates, we report the optimization of electron beam lithography and dry etching processes to fabricate sub-100 nm holes in pre-patterned Si (100) substrates with controlled size, shape, and periodicity. The pre-patterned silicon substrates underwent thorough ex situ chemical and in situ cleaning processes before the molecular beam epitaxy (MBE) growth. Finally, the MBE growth sequence of QDs on patterned silicon surface has shown highly selective formation of localized dome like nanostructures in patterned holes with 1 µm period.
A 3D AFM image of a single nanohole in silicon substrate with diameter and depth of about 70 nm.