Self-assembled growth of GaSb type II quantum ring structures

We demonstrate the self-assembled growth of GaSb quantum ring structures by molecular beam epitaxy. GaSb rings with the internal and external diameters of about 20 nm and 60 nm are successfully formed on GaAs by a growth procedure different from that for InAs rings reported earlier. The shape of GaSb structures can be controlled from a ring-like to an elongated disk-like geometry by changing the amount of deposited GaSb. A possible growth mechanism of GaSb rings is discussed. Photoluminescence spectra of the rings are presented and their features are discussed in terms of the type II band alignment, in which only holes are confined in the ring.