  We present a theoretical study of the energy spectrum of single electron and
hole states in quantum dots of annular geometry under a high magnetic field
along the ring axis in the frame of uncorrelated electron-hole theory. We
predict the periodic disappearance of the optical emission of the electron-hole
pair as the magnetic field increases, as a consequence of the finite height of
the barriers. The model has been applied to semiconductor rings of various
internal and external radii, giving as limiting cases the disk and antidot.
