Nanostructures in GaAs Fabricated by Molecular Beam Epitaxy

Molecular beam epitaxy (MBE) is essentially a controlled evaporation from various elemental sources in high vacuum onto a temperature- controlled single crystal substrate. The idea of epitaxy is that in the growing layer the newly arriving atoms incorporate at the precise positions established by the immediately preceding atomic layer. This epitaxial relationship extends even to a hetero-interface where a semiconducting GaAs layer abruptly changes to the higher bandgap more insulating material, AlAs, or to the alloy AlGaAs. Because GaAs, AlAs and AlGaAs have sufficiently similar crystal structures to one-another, MBE can produce single crystal layers of uniform and precisely controlled nano-thickness with no mismatched chemical bonds at the hetero-interfaces.