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.