Atomic force microscopy examination of elementary processes in metalorganic compound hydride epitaxy of GaAs-based nanoheterostructures

Elementary processes involved in low-pressure metalorganic compound hydride epitaxial growth of (Al, Ga, In)As heterostructures on misoriented GaAs(001) substrates have been studied using atomic force microscopy. It has been found that GaAs and AlGaAs epitaxial layers grow by a step–layered mechanism with the formation of microsteps. Pseudomorphic InGaAs/GaAs(001) layers also grow by this mechanism with the formation of macrosteps. However, if the thickness of the In$_{x}$Ga$_{1-x}$As/GaAs (001) pseudomorphic layer exceeds some critical value that depends on molar fraction $x$ of InAs entering into the solid solution, growth defects in the form of 3D islands are observed on the surface of the InGaAs layer with their density increasing with thickness of the InGaAs layer. Three-dimensional InGaAs islands grow owing to elastic stress relaxation in the InGaAs/GaAs(001) pseudomorphic layer by the Stranski–Krastanov mechanism.