Step instability of the In_0.2Ga_0.8As (001) surface during annealing

Abstract

Anisotropic evolution of the step edges on the compressive-strained In0.2Ga0.8As/GaAs(001) surface has been investigated by scanning tunneling microscopy (STM). The experiments suggest that step edges are indeed sinuous and protrude somewhere a little way along the [11̄0] direction, which is different from the classical waviness predicted by the theoretical model. We consider that the monatomic step edges undergo a morphological instability induced by the anisotropic diffusion of adatoms on the terrace during annealing, and we improve a kinetic model of step edge based on the classical Burton—Cabrera—Frank (BCF) model in order to determine the normal velocity of step enlargement. The results show that the normal velocity is proportional to the arc length of the peninsula, which is consistent with the first result of our kinetic model. Additionally, a significant phenomenon is an excess elongation along the [11̄0] direction at the top of the peninsula with a higher aspect ratio, which is attributed to the restriction of diffusion lengths.

Ripening of single-layer InGaAs islands on GaAs (001)

“…[11] The anisotropic diffusion of In-GaAs adatoms during annealing has been studied. [16] Reflection high-energy electron diffraction (RHEED) can be used to monitor the surface morphology in situ, [17] however, a real space image cannot be obtained by this method. During In-GaAs/GaAs annealing, higher As 4 beam equivalent pressure (BEP) will lead to small islands forming bigger ones and the surface coverage of islands will be lowered.…”