The influence of foreign species on the growth mode has been studied, with
special emphasis on the role of In. It is demonstrated that the growth mode
, i.e. 2D or 3D, first depends on the competing kinetics of Ga and N. In th
is view, we show that the surfactants modify both the Ga droplet formation
process and the N desorption rate. Next, we discuss the role of strain rela
xation in nitride heterostructures. In particular, we show that GaN and InG
aN can experience a Stranski-Krastanow growth mode leading to the formation
of quantum dots. A mechanism of quantum dot nucleation is proposed in the
case of GaN on AlN.