Temperature and Flux Dependence of Unstable Growth Mode on Patterned GaAs(001)

We report on the temperature and flux dependence of the growth mode of GaAs(001) during molecular beam epitaxy (MBE). Our previous results [1] for growth on patterned GaAs(001) surfaces showed that growth under typical conditions produces a transient instability. Lowering the temperature beneath $\sim $530 $^{o}$C at a growth rate of $\sim $ 0.3 nm/s produces a qualitative change in the way that the corrugations evolve. This temperature is close to that of a preroughening transition in the absence of growth [2], however on increasing the As2 flux the onset temperature for preroughening moves \textit{up}, while the onset temperature of the growth mode change moves \textit{down}. We correlate the change in growth mode with a change in the surface reconstruction. [1] H. C. Kan, S. Shah, Tadayyon-Eslami, and R. J. Phaneuf,. Phys. Rev. Lett, \textbf{92}, 146101, (2004). [2] V. P. Labella et al. Phys. Rev. Lett. \textbf{84}, 4152, (2003).