In situ probing at the growth temperature of the surface composition of (InGa)As and (InAl)As

A sudden shift from a bidimensional to a three-dimensional growth mode is observed when InAs is deposited by molecular-beam epitaxy on a pseudomorphic buffer layer grown on GaAs. The critical thickness for this shift is merely sensitive to the indium composition of the surface monolayer prior to growth. This property allows a direct in situ probing of the surface composition at the temperature of the growth. A detailed quantitative study of the surface segregation of indium atoms is performed for (InGa)As and (InAl)As alloys.