The so-called Stranski-Krastanov (S-K) growth technique is useful to fabricate quantum dots in large quantity. However, it is limited to hetero-epitaxial systems because the S-K growth method requires a lattice mismatch generally larger than 2% such as in InGaAs quantum nanostructures. We present a study on direct laser fabrication of a strain-free selfassembled GaAs nanostructures on GaAs(001) surfaces in a molecular beam epitaxy (MBE) growth reactor in-situ. This self-assembly is due to the rapid thermal relaxation of materials heated at the interference maxima lines that are created by overlapping two laser pulses interferentially on the epitaxial growth front inside an MBE growth reactor. The morphologies of the GaAs nanostructures are characterized by atomic force microscopy and field emission scanning electron microscopy (FESEM) while their stoichiometry has been characterized by low voltage energy dispersive X-ray spectroscopy that is coupled with FESEM. The morphological study indicates that the width and length of nanodots are a few tens of nanometers while their height is around ten nanometers. The nanodot dimensions are much smaller than the interferential period and the wavelength of laser used but comparable to findings in our recent reports of quantum dots produced by direct laser annealing. For the stoichiometry study of the nanostructures, low electron voltages less than 5 kilovolts have been used in order to enhance the surface sensitivity of the resulting X-ray fluorescence due to the small inelastic mean free path of electron (~ 4 nm at 3 kV) in GaAs. The stoichiometric analysis indicates that the relative gallium content increases with size. However, the nanodots’ arsenic content as well as the relative Ga composition reaches to those of GaAs substrate when the dot size becomes smaller than 100 nm. The chemical analysis suggests a novel route of strainfree semiconductor nanodots.

Date Published: 12 March 2015
PDF: 8 pages
Proc. SPIE 9352, Synthesis and Photonics of Nanoscale Materials XII, 93520P (12 March 2015); doi: 10.1117/12.2080296

Published in SPIE Proceedings Vol. 9352:
Synthesis and Photonics of Nanoscale Materials XII
Jan J. Dubowski; David B. Geohegan; Andrei V. Kabashin, Editor(s)