Complex quantum dot arrays formed by combination of self-organized anisotropic strain engineering and step engineering on shallow patterned substrates

Abstract

One-dimensional (In,Ga)As quantum dot (QD) arrays are created on planar singular, vicinal, and shallow mesa-patterned GaAs (100) substrates by self-organized anisotropic strain engineering of an (In,Ga)As∕GaAs quantum wire (QWR) superlattice template in molecular beam epitaxy. On planar singular substrates, highly uniform single QD arrays along [0−11] are formed. On shallow [0−11] and [011] stripe-patterned substrates, the generated type-A and -B steps distinctly affect the surface migration processes which are crucial for QWR template development, i.e., strain-gradient-driven In adatom migration along [011] and surface-reconstruction-induced Ga∕In adatom migration along [0−11]. In the presence of both type-A and -B steps on vicinal substrates misoriented towards [101], the direction of adatom migration is altered to rotate the QD arrays. This establishes the relationship between self-organized anisotropic strain and step engineering, which is exploited on shallow zigzag-patterned substrates for the realization of complex QD arrays and networks with well-positioned bends and branches, exhibiting high structural and optical quality.