Variation of surface composition during heteroepitaxy observed by coaxial impact collision ion scattering spectroscopy

Abstract

The heterointerface formation process, which is related to the lattice mismatch (ƒ) between the substrate and epitaxial layer, has been examined using coaxial impact collision ion scattering spectroscopy (CAICISS). The variation of the scattering intensity from the substrate atoms is measured during the initial stages of A1As/GaAs (ƒ=0.14%), GaAs/InP ( ƒ=4%) and GaAs/InAs (ƒ=7%) growths. In the case of A1As/GaAs growth, the scattering intensity from Ga atoms monotonically decreases as the A1As layer grows. However, in the cases of the GaAs/InP and GaAs/InAs growth, the scattering intensity from In atoms first decreases rapidly, then suddenly turns into a slow decrease. The turning point in the decrease of the scattering intensity agrees with the transition point of the growth mode from two-dimensional (2D) to 3D island growth for each system. These results show that the variation of the scattering intensity is a good indicator of the covering process of the substrate by the epitaxial layer which is strongly influenced by the lattice constant difference between the substrate and the epitaxial layer.