STRANSKI-KRASTANOV FORMATION OF INAS QUANTUM DOTS MONITORED DURING GROWTH BY REFLECTANCE ANISOTROPY SPECTROSCOPY AND SPECTROSCOPIC ELLIPSOMETRY

In this study the successful application of reflectance anisotropy spe ctroscopy (RAS) and spectroscopic ellipsometry (SE) for the in-situ in vestigation of InAs quantum dot growth on GaAs (001) in Stranski-Krast anov growth mode is reported. Both techniques provide the precise dete rmination of the growth mode transition from two-dimensional InAs laye r to three-dimensional island growth. In order to optimize the growth conditions, spectral and time-resolved measurements were performed for different growth parameters (temperatures, growth rates and V/III rat ios). For high temperature deposition large additional anisotropies, c aused by clusters elongated in the [110] direction were found. Decreas ing the deposition rate (0.5 to 0.125 ML/s) also results in the format ion of large clusters, as decreases in reflectivity due to larger stra y light losses prove. Finally, increasing the AsH3 partial pressure le ads to an earlier onset of island formation and an enhanced tendency f or cluster formation.