Growth modes of Ge on GaAs(001)

We have used low-energy electron microscopy to investigate the growth of Ge on GaAs(001)-c(2×8). Depending on the growth temperature we find a wide variety of growth modes: At 420°C growth proceeds layer by layer, with nucleation of two-dimensional (2D) islands smaller than 150 Å across. An increase of growth temperature to 450-480°C enhances surface diffusion and results in formation of large anisotropic 2D islands on wide terraces along with denuded zones - and step flow - along the step edges. Further temperature increase transforms the growth mode to step flow. At 540°C the growth mode becomes unstable, resulting in a roughening of the Ge surface.