1ST REAL-TIME OBSERVATION OF RECONSTRUCTION TRANSITION ASSOCIATED WITH GA DROPLET FORMATION AND ANNIHILATION DURING MOLECULAR-BEAM EPITAXY OF GAAS

The growing surface of GaAs(001) by molecular beam epitaxy under excess Ga flux and a continuous supply of As4 has been studied in-situ by scanning electron microscope and microprobe reflection high energy diffraction. Dynamical behavior of reconstruction transition associated with formation and annihilation of Ga droplets is observed in real time. It is shown that the transition between As- and Ga-stabilized surfaces occurs not uniformly but by the expansion of domains, the size of which is as large as on the order of a few hundreds mum. Ga droplets are formed inside the domains which show the Ga-stabilized reconstruction. There are two modes for the annihilation of Ga droplets, depending on the droplet density. The mechanisms for both the formation and the annihilation of domains and Ga droplets are discussed.