BOUND BIEXCITONS IN II-VI SEMICONDUCTORS

Biexcitons localized at neutral acceptor sites in the direct-gap II-VI semiconductors CdS and CdSe are identified with different spectroscop ic techniques such as photoluminescence, two-photon absorption and non linear quantum beat spectroscopy (NQBS). The NQBS offers the possibili ty to distinguish between quantum beats from a three-level system and polarization interference from independent two-level systems. The loca lized biexciton states are discussed in analogy with excited states of holes in neutral donor complexes.