Bound biexcitons in II-VI semiconductors

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