Effect of nitrogen on the InAs/GaAs quantum dot formation

We studied the influence of nitrogen incorporation on the InAsN/GaAs quantum dot formation using cross-sectional scanning tunneling microscopy. Upon nitrogen exposure during InAs growth, rather strong dissolution effects occur, leading to the formation of extended almost spherical InGaAs quantum dots with a low indium content and almost free of nitrogen. In this paper we will discuss in particular the detailed stoichiometry determination of the quantum dots. Furthermore, we will demonstrate that nitrogen atoms are located in the surrounding GaAs matrix. Indium atoms are found underneath the nominal base plane, where quantum dot growth started, demonstrating strong strain-induced intermixing already during quantum dot formation. The observed strong separation of indium and nitrogen is related to a rather low solubility of nitrogen within InAs as compared with GaAs. Finally, a schematic model for the growth of InAs and InAsN quantum dots in GaAs will be discussed in detail (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)