Modulation of electronic and optical properties of ZnO by inserting an ultrathin ZnX (XÂ = S, Se and Te) layer to form short-period (ZnO)5/(ZnX)1 superlattice

We demonstrate that the electronic and optical properties of ZnO can be improved by inserting into it with an ultrathin ZnX (X = S, Se and Te) layer to form short-period (ZnO)5/(ZnX)1 superlattices (SLs), which is a very promising substitution for p-type doping of ZnO. Results show that the SLs have some superior properties compared with bulk ZnO due to the strong modulation of the ZnX layer. The valence band arrangement of heavy hole (HH), light hole (LH) and crystal-field split-off hole is in the decreasing order from the valence band maximum (VBM) of (ZnO)5/(ZnX)1. The important band edge states are mainly determined by Zn and X atoms in the ZnX layer. The HH and LH have a very large effective mass along the c-axis of (ZnO)5/(ZnX)1. The peak value of dielectric function and absorption coefficient along the x/y direction at fundamental absorption edge is larger than that along the z direction, which indicates a transverse electric polarized light emission from c-plane.