Optical band gap of the filled tetrahedral semiconductor LiZnP

We report on the optical band gap of the filled tetrahedral (Nowotny-Juza) compound LiZnP [viewed as a zinc-blend-like (ZnP)^- lattice partially filled with He-like Li⁺ interstitials]. The band-gap nature of LiZnP predicted theoretically by an ``interstitial insertion rule'' is confirmed to be direct with a forbidden gap of 2.04±{}0.01 eV at room temperature. The typical resistivity, Hall mobility, and electron concentration at room temperature are of the order of 10 {Ω} cm, 25 cm²/V sec, and 10¹⁶ cm^-3, respectively. The empirical trend of band gaps between the filled tetrahedral and zinc-blende structures is discussed.