Nucleation of GaAs on Si: Experimental evidence for a three-dimensional critical transition

Abstract

The initial nucleation and growth stages of ultrathin GaAs films grown by molecular beam epitaxy upon Si(100) substrates are studied by high-resolution transmission electron microscopy. It is found that for a growth temperature of 405 °C, films initially nucleate as islands associated with steps on the substrate surface. In the earliest stages of growth, these islands are strained coherently to the substrate lattice, i.e., are free of misfit dislocations. As the islands grow, they become faulted. The transition from strained to dislocated states is shown to be a function of both the lateral and vertical island dimensions.