X‐Ray Spectroscopic Investigation of the Electronic Structure of A^IIB^IVC^V₂‐Type Semiconducting Phosphides

Abstract

a), M. A. BUNIN (a), 3%. A. BLOKHIN (a), V. I. MIXW (b), V. D. PROCHUKHAX (c), and G. K. AVERKIEVA (c) K-bands and absorption spectra of phosphorus and emission Le, 3-bands of silicon and phosphorusin MgSiP,, ZnSiP,, and CdSiP, are obtained. From a comparison of the spectra of different series and components in these compounds the influence of metal d-states on the valence band structure is studied. The admixture of phosphorus and zinc states to a metal d-state is estimated from the ZnSiP, spectra. Its smallness and the similarity of shape, position, and relative intensity of details of the corresponding spectra of all compounds are indicative of the fact that all metal d-states are only slightly hybridized with other states and only weakly affect the valence band structure. A sufficiently fair correspondence is revealed between the calculated spatial charge density distribution of valence electrons and the data about the localization and symmetry of electron states obtained from X-ray spectra. Good agreement between A E and E , is found ( A E is the energy gap between the emission ending and the onset of absorption of corrected P K-spectra, E , is the energy gap obtained by other physical methods). nOJIyYeHb1 K-nonocbI M CneKTpbI IIOrJIOJ.UeHMfi @OC@Opa, a TaHWe 3HMCCMOHHbIe Lz, 3-CneKTpOB pa3JIWlHbIX CepMfi M KOMnOHeHTOB 3 T M X COeEMHeHMfi II03BOJIHJlO MCCJIeXOBZiTb l) Prospekt Stilckki 192, 341090 Rostov-on-Don, USSR. 49 physica (b) loo/?

Electronic Structure of Triple Phosphides MgSiP2, ZnSiP2, and CdSiP2

“…For the experimental P-K-spectra of these compounds, more marked structures are typical, in particular, peak C, with a region of increased partial density of p-states of phosphorus corresponding to it, which is followed by a dip of N(E), separating this region from those whose maximal density coincides with the singularity of D 1 and D. The P-K-spectra of ZnSiP 2 and CdSiP 2 also possess a singularity A′, missing in the spectra from MgSiP 2 . In [28], this singularity was interpreted as a manifestation of the effect of pd-hybridization, which is in general supported by the present calculations as well. Note, that we may confidently argue that a difference in the position of peak A′ is accounted for by the difference in localization of the bands of d-states of Zn and Cd, while shifting peak A′ into the region of the main state density peak of s-band of phosphorus in CdSiP 2 is due to a higher hybridization of d-states of the cation with the anionic states, with this hybridization including interactions of sd-type in addition to pd-interactions.…”

“…2 are the x-ray and K-spectra from phosphorus and emission L 2,3 -spectra from Si and P, obtained in [28] with respect to the energy reference point. L 2,3 -bands from Si and P in the low-energy region contain a twopeak section, with the main peak A in P-L 2,3 has the same energy as the additional maximum (A) in Si-L 2,3 and another maximum B in Si-L 2,3 coincides with the wing of P-L 2,3 .…”

“…L 2,3 -bands from Si and P in the low-energy region contain a twopeak section, with the main peak A in P-L 2,3 has the same energy as the additional maximum (A) in Si-L 2,3 and another maximum B in Si-L 2,3 coincides with the wing of P-L 2,3 . The peculiar features mentioned were accounted for in [28] by the effect of hybridization of atomic states of phosphorus and silicon. The general structure and details of the spectrum are in a good agreement with the experiment.…”

“…2. Total (solid line) and projected state density, (p-P), x-ray L 2,3 -spectra from Si, P and K-spectrum from P-MgSiP 2 , ZnSiP 2 , and CdSiP 2 [28].…”

“…The experimental value of E g , however, derived from the optical transmission spectra, is 2.24 eV [29], the one obtained from an analysis of photoelectrical properties within the range 1-4 eV in the natural and polarized light below 300 K is 2.26 eV, while according to the data from x-ray absorption and emission spectra [28] it is 2.3 eV. The bottom of the conduction band in the center of the Brillouin zone exhibits symmetry Г 3c , so we could conclude that MgSiP 2 is a "pseudo-direct-gap" compound (E(Г 3с ) < E(Г 1с )), which is consistent with the results of other calculations [30].…”