Anisotropic Microstructure Development During the Reaction of Mg With GaAs
Steven W. Robey
Reaction of Mg with GaAs (001) surface occurs at substrate temperatures above 250 K and leads to 3D growth of an epitaxial, cubic reaction phase with a lattice constant of 0.62 + 0.02nm, 9% larger than GaAs. The resulting anistotropic, 3-demiensional (3D) heteroepitaxial microstructure was studied using in situ electron diffraction and Auger spectroscopy and ex situ atomic force microscopy (AFM). 3D structures develop that are elongated alone the GaAs  direction with aspect ratios (length-to-width) up to 20. These structures appear to be composed of isotropic islands from which elongated, tapered ridges extend in on direction along . Analysis of AFM images and size distributions suggest a critical size for the initiation of ridge formation and a discontinuous, stepwise ridge development. Potential origins of this interesting microstructure are discussed.