Self-organized superlattices along the [001] growth direction in In0.52Al0.48As layers grown on nominally (001) InP substrates by molecular beam epitaxy

Horizontal self-organized superlattice structures consisting of alternating In-rich and Al-rich layers formed naturally during solid-source molecular beam epitaxy (MBE) growth of In0.52Al0.48As on exactly (001) InP substrates, with In and Al fluxes unchanged. The growth temperatures were changed from 490 to 510 ∘C, the most commonly used growth temperature for In0.52Al0.48As alloy. No self-organized superlattices (SLs) were observed at the growth temperature 490 ∘C, and self-organized SLs were observed in InAlAs layers at growth temperatures ranging from 498 to 510 ∘C. The results show that the period of the SLs is very highly regular, with the value of ∼6 nm, and the composition of In or Al varies approximately sinusoidally along the [001] growth direction. The theoretical simulation results confirm that the In composition modulation amplitude is less than 0.02 relative the In composition of the In0.52Al0.48As lattice matched with the InP substrate. The influence of InAs self-organized quantum wires on the spontaneously formed InxAl1−xAs/InyAl1−yAs SLs was also studied and the formation of self-organized InxAl1−xAs/InyAl1−yAs SLs was attributed to the strain-mediated surface segregation process during MBE growth of In0.52Al0.48As alloy.