Temperature-Dependent Site Control of InAs/GaAs (001) Quantum Dots Using a Scanning Tunneling Microscopy Tip During Growth

Center for Collaborative Research, Anan National College of Technology, Anan, Tokushima, 774-0017 Japan.
Nanoscale Research Letters (Impact Factor: 2.78). 12/2010; 5(12):1930-1934. DOI: 10.1007/s11671-010-9802-z
Source: PubMed


Site-controlled InAs nano dots were successfully fabricated by a STMBE system (in situ scanning tunneling microscopy during molecular beam epitaxy growth) at substrate temperatures from 50 to 430°C. After 1.5 ML of the InAs wetting layer (WL) growth by ordinal Stranski-Krastanov dot fabrication procedures, we applied voltage at particular sites on the InAs WL, creating the site where In atoms, which were migrating on the WL, favored to congregate. At 240°C, InAs nano dots (width: 20-40 nm, height: 1.5-2.0 nm) were fabricated. At 430°C, InAs nano dots (width: 16-20 nm, height: 0.75-1.5 nm) were also fabricated. However, these dots were remained at least 40 s and collapsed less than 1000 s. Then, we fabricated InAs nano dots (width: 24-150 nm, height: 2.8-28 nm) at 300°C under In and As(4) irradiations. These were not collapsed and considered to high crystalline dots.

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    ABSTRACT: We have successfully confirmed that In atoms were favored to congregate inside hole structures, during In and As4 irradiations, by a STMBE system which was a scanning tunneling microscope located inside a molecular beam epitaxy growth chamber. After forming 1.5 monolayer of InAs wetting layer (WL) on a GaAs(001) surface, we applied voltage at a particular site on the WL during As4 irradiation at 300°C, creating hole structures (widths: 33–66.1nm, depths: 4.9–9.7nm). With the In and As4 irradiations, spontaneously, In atoms on the WL were congregated inside the holes, decreasing the volume of the hole structures. It was found that InAs growth rates inside the hole structures were 23.1–217 times larger than that at the WL growth region near the holes.
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