Epitaxial growth of Bi on GaAs(100) surfaces

Abstract

Bi layers deposited on (100) GaAs are investigated with low-energy electron diffraction, Auger electron spectroscopy, and electron energy-loss spectroscopy. The (100) substrates are prepared by simultaneous Ar+ sputtering and annealing. The deposition of Bi on room-temperature (100) GaAs eliminates the reconstruction spots at 0.5 monolayer. No long-range order is obtained in the room temperature grown Bi layer. Post-growth annealing at 250 °C restores long-range order and produces a sixfold symmetric hexagonal pattern characteristic of the rhombohedral structure of bulk Bi. The attenuation of the Auger peak intensities as a function of Bi thickness indicates that the film grows in a quasi-laminar fashion. The deposition of Bi on high-temperature (100) GaAs (250 °C) produces a two-dimensional ordered growth. The GaAs (4×6) structure is replaced by a (2×1) structure after deposition of one-half monolayer Bi. These (2×1) structure remains visible up to coverages of at least 25 monolayers. Auger measurements indicate island formation, while the sharpness of the electron diffraction spots indicates good crystallinity at the surface of the Bi crystal.