Self-organized Formation and XSTM-Characterization of GaSb/GaAs Quantum Rings

Abstract

In this chapter we discuss the details of the spatial structure of GaSb/GaAs(001) quantum rings, and how the observed nanostructures were achieved during the self-assembled growth and formation process. In contrast to the In(Ga)As/GaAs material system, for which thin capping of quantum dots followed by a longer growth interruption is necessary to initiate the quantum-dot to quantum-ring transformation, GaSb quantum rings occur already after the material deposition on GaAs(001), sometimes even without capping. Upon capping almost all quantum dots are transformed into quantum rings. The GaSb quantum rings are found to exhibit a clear central opening, which is filled by the pure GaAs capping material. The more direct formation process of the GaSb/GaAs(001) quantum rings can be understood by analyzing the details of the energies acting during the self-assembled growth. Hence, these more distinct quantum-ring structures are even more promising to show corresponding electronic states, as e.g., the Aharonov-Bohm effect.