MBE growth of self-assembled InGaAs quantum dots aligned along quasi-periodic multi-atomic steps on a vicinal (1 1 1)B GaAs surface

Abstract

Growth mechanisms of InGaAs three-dimensional (3D) islands formed on vicinal (1 1 1)B GaAs surfaces with multi-atomic steps are studied by examining surface morphologies of In x Ga 1− x As layers having various In contents x and/or nominal thickness d. When an InGaAs layer with x = 0.29 and d = 3 nm was deposited by molecular beam epitaxy (MBE), 3D islands with lateral sizes of about 40 nm, almost twice as much as the average period (∼20 nm) of underlying GaAs steps, were formed and densely aligned along the steps. A nearly flat surface was formed, when an InGaAs layer with x = 0.10 and d = 3 nm was deposited. In case of d = 2 nm and x = 0.30 , smaller 3D islands were densely formed and their lateral size perpendicular to the steps was typically about 20 nm. Such 3D islands were hardly found when d = 2 nm and x = 0.55 . These results support our hypothetical model that the 3D island formation is induced by the abrupt increase in strain energy resulting from the coherent connection of a pair of InGaAs wire-like structures on a pair of adjacent GaAs multi-atomic steps.