Scanning electron microscopy of InAs aggregation on GaAs vicinal surfaces in molecular beam epitaxy

Abstract The aggregation process of InAs on GaAs(1 0 0) vicinal surfaces 0.3° inclined toward the [01¯1] direction during molecular beam epitaxy and annealing at 480°C were studied in situ by scanning electron microscopy and ex situ by atomic force microscopy. When the indium beam was supplied by 0.2 ML pulses interrupted by 90 s under constant arsenic flux, only monatomic steps were observed on the surface even up to a total supply of 2 ML InAs. After uniform and high density islands were formed by a continuous deposition of 2 ML InAs, annealing was conducted which greatly reduced the island density while the sizes of remaining islands did not increase appreciably. Obvious step advance occurred under annealing as indium atoms were supplied into the step edges from the decomposing InAs islands. It was observed in real time that as the growth of InAs was proceeded, the height to base diameter ratio of the InAs island increased before they relax or coalesce with neighboring islands.