THE INITIAL-STAGES OF GEGAAS(100) INTERFACE FORMATION STUDIED BY REFLECTANCE ANISOTROPY SPECTROSCOPY AND LOW-ENERGY-ELECTRON DIFFRACTION

The initial stages of formation of the Ge-GaAs(100) interface, during monolayer Ge deposition and annealing are studied by reflectance aniso tropy spectroscopy (RAS) and low-energy electron diffraction (LEED). C hanges in the reflectance anisotropy spectra show that interface under goes dramatic structural modification as it is annealed. After deposit ion of approximately 1 ML of Ge onto a room temperature GaAs(100)-(2 x 4) substrate followed by annealing, increased (1 x 2) ordering was ob served up to an annealing temperature of 875 K, where a well-ordered ( 1 x 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 r eflectance anisotropy spectra which are associated with Cc-Ca dimer fo rmation. Upon deposition of a further 1.7 ML of Ge and annealing to 84 0 K, a (1 x 2) LEED pattern is still observed, but now with some disor der. The RA spectra for this surface displays large differences compar ed to the lower coverage (1 x 2) surface suggesting a different termin ation which we associate with As interdiffusion, in agreement with pre vious work [2]. (C) 1998 Elsevier Science B.V. All rights reserved.