Surface processes during growth of InAs/GaAs quantum dot structures monitored by reflectance anisotropy spectroscopy

The time resolved reflectance anisotropy spectroscopy (RAS) measurement at 4.2 eV was used for the optimization of technological parameters for Stranski-Krastanow quantum dot (QD) formation. TMIn dosage and waiting time following InAs deposition during which QD formation takes place were optimized. RAS measurement helps us to study the MOVPE surface processes such as QD formation, dissolution of In from InAs QDs during the growth of GaAs capping layer or recovery of epitaxial surface from As deficiency, when As partial pressure is increased. We have shown, that the recovery of epitaxial surface from As deficiency is rather a slow process of the order of tens of seconds. We have for the first time observed in situ the mechanism of In atoms migration from QDs during GaAs capping layer growth. First the GaAs layer is formed and then the In migration from QDs follows. These two processes do not start at the same time, the In dissolution is delayed. Conclusions extracted from RAS measurement are in agreement with photoluminescence results. (C) 2009 Elsevier B.V. All rights reserved.