New selective molecular-beam epitaxial growth method for direct formation of GaAs quantum dots

Abstract

Numerous GaAs epitaxial microcrystals having an average base size of 700 Å×700 Å surrounded mainly by (111) and (110) facets were fabricated on a sulfer-terminated (S-terminated) GaAs (001) substrate by sequentially supplying Ga and As molecular beams. The S-terminated GaAs (001) surface was produced by exposing the surface to a sulfur vapor in the molecular-beam epitaxy system immediately after obtaining a Ga-stabilized surface. The growth of GaAs microcrystals on the S-terminated substrate is caused by a vapor–liquid–solid mechanism. The process consists of forming Ga droplets on the inert surface and reacting the droplets with As to produce GaAs microcrystals. This method termed droplet epitaxy is thought to be a promising growth method for fabricating the GaAs quantum dots.