Indium incorporation in In-rich In_xGa_(1-x)As/GaAs layers grown by low-pressure metalorganic vapor-phase epitaxy and its influence on the growth of self-assembled quantum dots

摘要

We report a study of the interaction between In-alkyls and Ga-alkyls during the low-pressure metalorganic vapor-phase epitaxy (LP-MOVPE) of In-rich In_xGa_(1-x)As layers around 500℃. The structural properties of the layers are determined by analyzing their transmission electron microscopy contrast. The evolution of growth rate and composition of the In_xGa_(1-x)As layers grown under various Ga precursor flow rates is interpreted by modeling the growth kinetics. This approach allows us to identify the main alkyl species present at the growth interface. In particular, it is shown that the presence of monomethylgallium and dimethylgallium on the growth surface enhances the incorporation of In in the layers, promoting the removal of the methyl radical from the monomethylindium molecules by methyl-exchange reactions. This mechanism plays a dominant role in the incorporation of In in our growth conditions: more than 70% of the In atoms incorporated in the layers undergo a methyl-exchange reaction on the growth surface. The structural properties of quantum dots (QDs) grown by depositing In_xGa_(1-x)As layers with various In compositions are compared. An increase of the gallium precursor flow rate during the growth of the QDs is shown to increase their density (between a few 10~9 and a few 10~(10) cm~(-2)) and to modify strongly their structural properties.