Spontaneous decomposition and ordering during epitaxial growth

The growth of alloy layers by molecular-beam deposition is considered theor etically, with emphasis on the connection between local variations in the c omposition and surface roughening. For alloy layers mismatched to the subst rate, the elastic fields generated by the mismatch couple with the elastic fields generated by compositional inhomogeneities, leading to a joint compo sitional/morphological instability under certain growth conditions. We show that the non-equilibrium nature of the growth leads to a competition betwe en these strain relieving mechanisms, the alloy thermodynamics and the kine tics of the deposition process. We show explicitly how our theory is applie d to real systems, taking InGaAs layers as an example. The theory is genera lized to include the formation of atomically ordered phases during growth, by focusing on the experimentally observed relation between ordering and lo cal surface misorientations. (C) 1999 Elsevier Science S.A. All rights rese rved.