Step bunching on {111} facets in the selective growth of GaAs by metalorganic vapor phase epitaxy

Step bunching on the {111}A and {111}B side facets formed in the selective growth of GaAs on (001) GaAs substrates by metalorganic vapor phase epitaxy is investigated by atomic force microscopy. It is shown that the bunching characteristics are determined by the misalignment angle of the selective growth mask from [110] and [110] directions of the substrate: Bunched steps are clearly observed when the misalignment angle is more than 0.25°, but their density decreases below this angle, and they completely disappear at 0.008°. Bunching behavior on the {111} facets is compared with that on (001) surfaces and the bunching mechanism is discussed.