In situ scanning tunneling microscopy of InAs quantum dots on GaAs( 0 0 1 ) during molecular beam epitaxial growth
Abstract Arrays of InAs quantum dots (QDs) have been studied using in situ scanning tunneling microscopy (STM) during their growth by molecular beam epitaxy on GaAs(0 0 1). At a substrate temperature of 400 °C under As 4 flux, both the QDs and the underlying step-terrace structure of the wetting layer (WL) are found to be static, with neither step-flow nor QD ripening observed. Higher resolution images of the mature WL show slightly different [1 1 0] periodicities to those observed in quenched STM studies.
In situ study of low-temperature growth and Mn, Si, Sn doping of GaAs (0 0 1) in molecular beam epitaxy
Abstract Low-temperature growth of GaAs was investigated using in situ reflectance anisotropy spectroscopy (RAS) for the first time. RAS indicates that the surface during growth is mostly unreconstructed with many dangling bonds. Above a critical thickness anisotropic roughening occurs. When doped with Mn, Si, and Sn the RAS signal showed only contributions due to surface band bending from doping. At very high concentrations the spectra change, indicating a transition from doping to alloying. Alloying occurred above 2–3% Mn or for more than 1% Sn incorporation.
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.