Structure of clean and arsenic-covered GaN(0 0 0 1) surfaces
Abstract The effect of trace arsenic on the growth and surface structure of GaN(0 0 0 1) has been studied. We find that a partial pressure of only 10 −9  Torr of arsenic during molecular beam epitaxial growth significantly modifies the growth kinetics. Such a small background pressure of arsenic leads to an arsenic-terminated surface displaying a 2×2 reconstruction during growth which is absent for the clean surface. First-principles theoretical calculations show that As-terminated surfaces are energetically more favorable than Ga-terminated surfaces for arsenic pressures of 10 −9  Torr, and structural models for the As-adatom 2×2 reconstruction are presented.
SURFACE MORPHOLOGY OF GaN SURFACES DURING MOLECULAR BEAM EPITAXY
The reconstruction and surface morphology of gallium nitride (0001) and $(000\bar 1)$ surfaces are studied using scanning probe microscopy and reflection high energy electron diffraction. Results for bare GaN surfaces are summarized, and changes in the surface structure and morphology due to codeposition of indium or magnesium during growth are discussed.
Surface reconstructions and growth mode transitions of AlAs(100)
Abstract The surface reconstructions of AlAs(100) layers grown by molecular beam epitaxy (MBE) on GaAs(100) were mapped as a function of substrate temperature and arsenic flux. Three main reconstructions were observed - a c (4 × 4) at lower temperatures and higher arsenic fluxes, a (2 × 4) at middle temperatures, and a (3 × 2) at higher temperatures and lower arsenic fluxes. Growth of AlAs on AlAs(100) is layer-by-layer for the high temperature and low temperature reconstructions. In the mid-temperature region, AlAs grows rough on (2 × 4) reconstructed AlAs(100) as indicated by rapidly damped reflection high-energy electron diffraction (RHEED) intensity oscillations and the appearance of three-dimensional (3D) features. The addition of fractional layers of Ga enhances the smooth growth of AlAs. A metastable (5 × 2) reconstruction was observed when a fraction of a layer of Ga was present on the surface. The results indicate that Ga segregates during the growth of AlAs on GaAs(100) at temperatures at least as low as 500°C, and that annealing at temperatures above 700°C removes most of the Ga from the surface.