Improved uniformity and carrier confinement of lateral dot-like nanostructures formed in triangular-shaped hole arrays on patterned GaAs (311)A

We study the formation of dot-like nanostructures by molecular beam epitaxy (MBE) on GaAs (311)A substrates patterned with triangular-shaped hole arrays. Ridge-type dot arrays generated on µm-sized patterns fabricated by optical lithography and wet chemical etching reveal three dimensional carrier confinement by cathodoluminescence (CL) mapping in the triangular tips formed between the holes on the top surface. The overall structure, however, exhibits rather complex CL emission due to parasitic quantum wells on the slow growing sidewalls of the holes. In contrast, very uniform lateral dot-like nanostructures are produced at the fast growing sidewalls and corners of sub-mm-scale triangular hole arrays fabricated by electron beam lithography and reactive ion etching. The ridge-like structures on the top surface and the slow growing sidewalls in the holes completely smear out and the CL spectra of the dot arrays are composed of only two narrow lines from the quantum-well layers and the dot-like fast growing sidewalls or corners of the holes which they surround. The lateral carrier confinement energy in the dots exceeds 100 meV. Thus, very uniform and dense dot-like nanostructures with large confinement energy are formed by pattern size reduction based on the unique formation of the fast growing mesa sidewall on patterned GaAs (311)A substrates.