Classification of Surface Defects on GaAs Grown by Molecular Beam Epitaxy

Abstract

Surface defects on grown by molecular beam epitaxy (MBE) have been classified and analyzed using an image analyzing system with Nomarski contrast microscope, a scanning electron microscopy (SEM), and an Auger electron spectroscopy (AES). Nine types of defects were observed. Four of them were usually observed on typical epitaxials. Density distribution histograms of surface defects on typical revealed four distinct peaks. The first peak corresponds to oval defects with a median size of 100 μm2. The second peak corresponds to defects of 5 μm2, which originate in contamination on the substrate surface. The third peak corresponds to circular defects of 10 μm2 The fourth peak corresponds to defects, 1 μm2 or less, which originate in minute irregularities such as dislocations in the substrate. Although the defects of 100 μm2 and of 10 μm2 were quite different in shape from each other, their density proved to be strongly dependent on growth conditions and the number of growth runs. Therefore, it is inferred that they are due to the different origins in the Ga source such as Ga oxide and Ga spitting.