Electronic band structures of filled tetrahedral semiconductor LiMgP and zinc-blende AlP

The band structures of the filled tetrahedral semiconductor LiMgP and zinc-blende AlP were studied using the full potential linearized augmented plane wave method (FP-LAPW). The conduction band modifications of LiMgP, compared to its ‘parent’ zinc-blende analog AlP, are discussed. It was found that the conduction band valleys of LiMgP follow the X–Γ–L ordering of increasing energy for both α (Li+ near the anion) and β (Li+ near the cation) phases, whereas AlP has the X–L–Γ ordering, and the differences between the direct (Γ–Γ) and indirect (Γ–X) gaps decrease in the α and β-LiMgP, compared to AlP. The interstitial insertion of closed-shell Li+ ion is a possible method to change the direct–indirect gap nature, but the ‘interstitial insertion rule’ cannot be applied in predicting all conduction band modifications of LiMgP, relative to AlP. The total energy calculations show the α phase to be more stable than the β phase for LiMgP.