Direct-Gap Reduction and Valence-Band Splitting of Ordered Indirect-Gap AlInP2 Studied by Polarized Piezoreflectance

The order-dependent direct-gap reduction and valence-band splitting in spontaneously ordered indirect-gap AlInP2 are determined by polarized piezoreflectance spectroscopy at room temperature. The experimentally deduced values of the ratio of band-gap reduction to crystal field splitting for the perfectly ordered alloys, ζ=-ΔEg(1)/ΔCF(1)=1.15, and the ratio of band-gap reduction to the ordering change of spin-orbit splitting between the perfectly ordered and random alloys, ξ=-ΔEg(1)/[ΔSO(1)-ΔSO(0)]=8.24, are in good agreement with the recent theoretically calculated value of 1.13 and 13.5, respectively, by [S. H. Wei and A. Zunger. Phys. Rev. B 57, (1998) 8983] but are much larger than those of the previous report by [M. Schubert et al..: Phys. Rev. B 54 (1996) 17616] using dark-field spectroscopy.