Band-Structure Modification by Insertion of Small Atoms at Tetrahedral Interstitial Sites in Zinc-Blende-Like Lattice

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LiZnP can be viewed as a zinc-blende-like (ZnP)^- lattice filled partially with He-like Li^+ interstitials. We have grown LiZnP by directional solidification of Li, Zn, and P using a tantalum crucible. The grown crystals were transparent red in color and showed the antifluorite structure with a=5.765<plus-minus>0.005A. The differential thermal analysis show an endothermic reaction around 950^ﾟC, indicating the melting point or the decomposition of the crystal. LiZnP was confirmed to be a semiconductor with direct band gap 2.04 to 2.12 eV at a temperature ranging from 295 to 95 K. As grown-crystals are p-type except for some crystals. The typical resistivity, Hall mobility, and carrier concentration at room temperature are of the order of 10^<-1>-10 OMEGAcm, 1-10 cm^2/Vs and 10^<16>-10^<18> cm^<-3>, respectively. The radiative recombination related to a native defect in LiZnP was studied at 77K using photoluminescence (PL) technique. One type of PL emission consists of two peaks : One is a peak 615nm (2.02 eV) associated with a phosphorus vacancy (lying at 110meV below the conduction band) -valence band transition and the other a broad peak at 848nm (1.46eV) associated with phosphorus vacancy-acceptor complex. Another type exhibits an only broad emission around 830 nm. The origin of the broad emissions observed in both types is likely to be identical essentially.