Atomic-scale structure of self-assembled In(Ga)As quantum rings in GaAs

P. Offermans, P.M. Koenraad, J.H. Wolter, D. Granados, J.M. Garcia, V. Fomin, V.N. Gladilin, J.T. Devreese

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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.
Original languageEnglish
Article number131902
Pages (from-to)131902-1/3
Number of pages3
JournalApplied Physics Letters
Issue number13
Publication statusPublished - 2005


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