Epitaxial lateral overgrowths of GaAs on (001) GaAs substrates by LPE: Growth behavior and mechanism

Abstract

The growth behavior and mechanism of epitaxial lateral overgrowths (ELO) of GaAs on (001) GaAs substrates are investigated. It is found that the lateral growth shows a strong dependence on the orientation of its aligned seed. The lateral growth is slowest when its aligned seed is oriented in any of the [100], [110], [010], [ 1 10] or their equivalent directions. However, it increases sharply when its aligned seed is tilted away from the above orientations. Monomolecular growth steps with strong contrast and high lateral spatial resolution on the surface were successfully observed using a Nomarski differential interference contrast microscope with an image processor. Their average propagation velocity is estimated to be in the range of 3–30 μm/s. It has been found that the surface of the ELO layer is extremely flat on an atomic scale. The experimental results indicate that vertical growth is mainly determined by the propagation of steps that originate from their source. On the other hand, lateral growth is limited by the diffusion of As in Ga solution until {111} or {001} facets appear on the lateral growth front. Then, the growth becomes limited kinetic processes. It Is concluded that substrates of (001) GaAs as well as (111) GaAs are suitable for achieving a very smooth ELO layer with a large ratio of the lateral growth width to the vertical growth thickness.