Growth dynamics of InGaAs by MBE: process simulation and theoretical analysis

摘要

In the InGaAs materials system, the perfection is intrinsically controlled by the surface segregation of In due to its larger atomic size compared to Ga. In spite of several experimental investigations, there is a lack of a thorough understanding of the underlying surface dynamic processes and their interplay. In this work, a rate equation model is developed including several physically sound surface processes such as segregation from the crystalline layer to a surface riding In segregated layer and incorporation from the segregated In layer to crystalline layer. The rate of the processes are assumed Arrhenius-type with concentration-dependent activation energies. The simulated In incorporation coefficient versus substrate temperature is in excellent agreement with experimental data for various As overpressure. For a constant As overpressure, In incorporation decreases with increasing temperature. For a constant temperature, In incorporation increases with increasing As overpressure. The In desorption versus time results from experiments and our simulation match very well. The desorption process has two components, one arising from the physisorbed layer of In and the other from the surface of the crystal. The activation energy for these processes for an isolated In adatom are 0.18 and 2.6 eV, respectively. These observations are explained based on the interplay of competing surface processes such as segregation and incorporation.