Isoelectronic oxygen in II-VI semiconductors

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Abstract
The properties of isoelectronic oxygen in II-VI semiconductors were studied by photoluminescence measurements. It was found that oxygen in CdTe, CdS, and ZnS can act as an acceptor as well as in ZnSe, and that the acceptor levels of oxygen in CdTe, CdSe, and ZnS are shallower than those of typical acceptors such as Na. Charge transfer from the host lattice to the oxygen atom may play an important role in oxygen acting as an acceptor. Based on the charge-transfer model, it can be qualitatively interpreted that there are two roles of oxygen in II-VI compounds: acting as an acceptor or as a trap, and that they are classified by the ionicity of the compound. We also now understand better the chemical trend of the oxygen-acceptor levels becoming more shallow compared to the typical acceptors.