Non-stoichiometry effects on electrical and luminescence properties of the layered oxysulfide (LaO)CuS

The layered oxysulfide (LaO)CuS is a wide-gap semiconductor. In general, the wide-gap semiconductor has strong mono-polarity and non-stoichiometry which affect their physical properties. In this study, the relation between the non-stoichiometry of (LaO)CuS and their physical properties has been investigated. Several kinds of non-stoichiometric samples were prepared. In the Cu non-stoichiometry, (LaO)CuS can accommodate the excess Cu in preference to a deficiency. In the La and S non-stoichiometric samples, deficiencies are preferred. The Cu and S non-stoichiometry affects their electrical and emission properties as expected from the valence band structure. It should be noted that the La non-stoichiometry is also quite effective on the band edge emission and the resistivity as well as other non-stoichiometry. These results reveal that not only Cu but also La deficiency is important in controlling the physical properties.