The Role of Stress and Stress Anisotropy in Semiconductor Nanostructures Self-Assembling

Abstract

Stress relaxation during growth of lattice-mismatched III-V semiconductor compounds can induce the formation of nanostructures. By means of an in situ and in real-time stress measurements technique, we have followed the nanostructures self-assembling process in different heteroepitaxial semiconductor systems. After explaining the basis of these in situ stress measurements, the results we have obtained on quantum dots and quantum wires formation in the systems InAs/GaAs (001), InAs/InP (001) and GaSb/GaAs (001) will be presented, together with the similarities and differences between the three systems. In the InAs/GaAs (001) system, where quantum dots are obtained, we have detected a limited In incorporation during the pseudomorphic growth of InAs on GaAs. The well known In segregation process is originated by the incorporation of this floating In during GaAs overgrowth. For InAs/InP, we have found the existence of a higher stress along [110] direction than along [1-10] when growing this system by standard molecular beam epitaxy conditions. This stress anisotropy leads to the formation of quantum wires instead of quantum dots in this system. Finally, during growth of the GaSb/GaAs (001) system quantum dots are also formed. In this case, the stress measurements show clearly the presence of mass transport coming from the wetting layer during dots formation.