Unstable growth on rough surfaces

We present experimental data for the morphological evolution of InAs buffer layers which are interpreted using continuum equations of motion and kinetic Monte Carlo simulations. Our analysis reveals the presence of an instability even as an initially rough surface smooths during growth. This instability is due to the step-edge barrier and causes a characteristic length to emerge while the surface roughness is decreasing, well before the formation of the mounds. The smoothing is well described by a linear continuum equation identical to that which describes the early stages of spinodal decomposition and has important practical implications for the growth of device buffer layers. [S0031-9007(98)07810-7].