Large size self-assembled quantum rings: quantum size effect and modulation on the surface diffusion

We demonstrate experimentally the submicron size self-assembled (SA) GaAs quantum rings (QRs) by quantum size effect (QSE). An ultrathin In(0.1) Ga(0.9)As layer with different thickness is deposited on the GaAs to modulate the surface nucleus diffusion barrier, and then the SA QRs are grown. It is found that the density of QRs is affected significantly by the thickness of inserted In(0.1) Ga(0.9)As, and the diffusion barrier modulation reflects mainly on the first five monolayer . The physical mechanism behind is discussed. The further analysis shows that about 160 meV decrease in diffusion barrier can be achieved, which allows the SA QRs with density of as low as one QR per 6 μm(2). Finally, the QRs with diameters of 438 nm and outer diameters of 736 nm are fabricated using QSE.