The initial stages of Ge–GaAs(100) interface formation studied by reflectance anisotropy spectroscopy and low-energy electron diffraction

Abstract

The initial stages of formation of the Ge–GaAs(100) interface, during monolayer Ge deposition and annealing are studied by reflectance anisotropy spectroscopy (RAS) and low-energy electron diffraction (LEED). Changes in the reflectance anisotropy spectra show that interface undergoes dramatic structural modification as it is annealed. After deposition of approximately 1 ML of Ge onto a room temperature GaAs(100)-(2×4) substrate followed by annealing, increased (1×2) ordering was observed up to an annealing temperature of 875 K, where a well-ordered (1×2) LEED pattern previously found to consist of Ge–Ga dimers X.-S. Wang, K. Self, V. Bressler-Hill, R. Mabouidian, W.H. Weinberg, Phys. Rev. B 49 (1994) 4775. was observed. Features are identified in the reflectance anisotropy spectra which are associated with Ge–Ga dimer formation. Upon deposition of a further 1.7 ML of Ge and annealing to 840 K, a (1×2) LEED pattern is still observed, but now with some disorder. The RA spectra for this surface displays large differences compared to the lower coverage (1×2) surface suggesting a different termination which we associate with As interdiffusion, in agreement with previous work [2].