Observation of Reentrant 2D to 3D Morphology Transition in Highly Strained Epitaxy: InAs on GaAs

The two-dimensional (2D) to three-dimensional (3D) transition in highly strained growth of InAs of GaAs(001) is investigated using in situ scanning tunneling microscopy and photoluminescence spectroscopy. Remarkably, InAs structural features up to five monolayers (ML) high appear at $\sim 1.25\mathrm{ML}$, disappear, and reappear prior to the onset of well-developed 3D islands at 1.57 ML, thus manifesting a hitherto unrecognized reentrant behavior in the formation of 3D islands. The results provide new insights into the long-standing problem of the kinetic aspects of 2D to 3D morphology change not embodied in the widely encountered Stranski-Krastanow growth mode.