We present an atomic-scale analysis of the indium distribution of self-assembled In(Ga)As quantum rings (QRs) which are formed from InAs quantum dots by capping with a thin layer of GaAs and subsequent annealing. We find that the size and shape of QRs as observed by cross-sectional scanning tunneling microscopy (X-STM) deviate substantially from the ring-shaped islands as observed by atomic force microscopy on the surface of uncapped QR structures. We show unambiguously that X-STM images the remaining quantum dot material whereas the AFM images the erupted quantum dot material. The remaining dot material shows an asymmetric indium-rich crater-like shape with a depression rather than an opening at the center and is responsible for the observed electronic properties of QR structures. These quantum craters have an indium concentration of about 55% and a diameter of about 20 nm which is consistent with the observed electronic radius of QR structures. © 2005 American Institute of Physics.
Offermans, P., Koenraad, P. M., Wolter, J. H., Granados, D., Garcia, J. M., Fomin, V., Gladilin, V. N., & Devreese, J. T. (2005). Atomic-scale structure of self-assembled In(Ga)As quantum rings in GaAs. Applied Physics Letters, 87(13), 131902-1/3. . https://doi.org/10.1063/1.2058212