Observation of ordering and phase separation in InxGa1−xN layers

A series of InGaN layers grown by metalorganic vapour deposition and molecular beam epitaxy have been investigated by transmission electron microscopy (TEM). It is shown that for In concentrations lower than 15%, the InGaN layers has a crystalline quality comparable to that of the underlying thick GaN buffer layer. Both ordering inside the InGaN films and phase separation have been observed when the In concentration was brought over 20%; they are found to depend on the growth conditions as well.