E. Steimetz et al., OPTICAL MONITORING OF THE DEVELOPMENT OF INAS QUANTUM DOTS ON GAAS(001) BY REFLECTANCE ANISOTROPY SPECTROSCOPY, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 14(4), 1996, pp. 3058-3064
Reflectance anisotropy spectroscopy (RAS) in combination with reflecti
on high-energy electron diffraction (RHEED) was used to study in situ
the initial steps of molecular beam epitaxial growth of InAs on GaAs(0
01). Due to the large lattice mismatch InAs is known to grow in Strans
ki-Krastanov mode leading to the formation of quantum dots after the t
ransition from two- to three-dimensional growth mode. In this article
the precise determination of the growth mode transition and the subseq
uent development of the islands have been of particular interest. Duri
ng the growth of the two-dimensional InAs layer, the RHEED-pattern cha
nged from the c(4x4) of the clean GaAs to a (1x3) surface reconstructi
on. Accordingly, the RAS-spectra, taken every 0.2 ML, indicate changes
of the As-dimer configuration. At 1.8 ML (spotty RHEED-pattern) a sat
uration of the intensity of the dimer related RAS-signal around 2.6 eV
was found. The relaxation of the InAs layer and the formation of the
quantum dots was followed by time-resolved RAS at 2.6 and 4 eV. It is
shown here, that the time constant of this process, the thickness of t
he InAs wetting layer and the equilibrium morphology of the islands ar
e strongly temperature dependent. The remaining equilibrium InAs wetti
ng layer thickness at the surface was estimated to be about 1 ML (0.8
ML at 625 K and 1.2 ML at 725 K). (C) 1996 American Vacuum Society.