Band alignment in ZnSe Se quantum-well structures

We present a magneto-optical study of ZnSe/(Formula presented) Se quantum-well structures in which a suitable choice of the Cd composition leads to a system that is type I at zero magnetic field. When a magnetic field is applied perpendicular to the layers of the structure, the band edges split in such a way as to make the upper (Formula presented) (+, +) exciton transition type II, while the ground state (Formula presented) (-, -) exciton component remains type I at all field values. This alignment reduces the probability for carrier relaxation from the higher-energy exciton component and opens the possibility of hole-spin population inversion via optical pumping.