SURFACE MORPHOLOGIES OF GaAs LAYERS GROWN BY ARSENIC-PRESSURE-CONTROLLED MOLECULAR BEAM EPITAXY.

Surface morphologies of the molecular beam epitaxy (MBE)-grown GaAs layers using background arsenic-pressure-control method were investigated. The growth parameters, such as substrate temperatures, growth rates, epilayer thicknesses, As/Ga ratios, doping concentrations, substrate types, etc. , are related to the observed oval defect density. Protrusions and Ga-droplet induced oval defects were formed during growth. The origin of the oval defects in our system is found to be the gallium oxide, not Ga 'splitting' from the effusion cell. Surface preparations are also another important factor in reducing the oval defect density. Special triangular pyramidal defects with concave or acute top surfaces were found. They have the same major axis as oval defects. Also found were defects with perpendicular orientation to the oval defects. Such defects are attributed to contaminations on the surface and can be eliminated.