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HL: Fachverband Halbleiterphysik

HL 86: Quantum Dots: Growth and Characterization

HL 86.4: Vortrag

Freitag, 18. März 2011, 11:00–11:15, FOE Anorg

MBE growth of InAs quantum dots and dashes grown on (100) silicon substrates — •Tariq Al Zoubi, Muhammad Usman, Mohamed Benyoucef, and Johann Peter Reithmaier — Technische Physik, Institute of Nanostructure Technologies and Analytics, University of Kassel, D-34132 Kassel, Germany

Self assembled InAs quantum dots (QDs) are grown by solid source molecular beam epitaxy after deposition of a 50 nm silicon buffer layer on (100) Si substrates using Stranski-Krastanov (SK) growth mode. Reflection high energy electron diffraction (RHEED) streak patterns confirm that the combination of the atomic hydrogen at 500 °C followed by thermal desorption at 900 °C is an efficient surface cleaning method. The evolution of size, density and shape of the QDs are ex-situ characterized by atomic-force microscopy (AFM). Different growth parameters such as InAs coverage, growth temperature, In-growth rate and V/III ratio are examined on differently prepared silicon surfaces including ex- and in-situ cleaning procedures. Additional improvement for the cleaning and growth is achieved by exposing the Si surface with Ga at low fluxes. The Ga treatment at a temperature of 560 °C for two minutes results in a strong reduction of the lateral size of InAs QDs and a significant enhancement of the homogeneity of the dot size and distribution. The InAs QDs density is strongly increased from 10^8 to 10^11 cm^-2 for V/III ratios in the range of 15-35, respectively. InAs QD formations are not observed at temperatures as high as 500 °C. Moreover, InAs quantum dashes are observed at higher In-growth rate of 0.3 ML/s.