On the origin of the kinetic growth instability of homoepitaxy on Si(001)

The recently observed kinetic growth instability of homoepitaxial layers on Si(001) was investigated by in-situ scanning tunneling microscopy (STM ) experiments. In the step-flow regime the instability consists of straight step bunches, and it vanishes both during two-dimensional (2-D) island growth and at high temperatures. Kinetic Monte Carlo (KMC) simulations were performed to identify the dominating mechanism causing the instability. Strong evidence for the presence of an asymmetric step-edge barrier with the behavior of an inverse Ehrlich–Schwoebel barrier is found. Comparison between the experiments and the simulations reveal that only double atomic height DB steps, which form kinetically in a rather narrow temperature range, develop this type of step-edge barrier.