Electroreflectance Spectra and Energy Band Structure of CdSnP₂

Abstract

E. I. LEONOV (c), V. M. ORLOV (c), V. A. CHALDYSHEV (b), and A. SILEIKA (a)The electroreflectance spectra of CdSnP, chalcopyrite single crystals have been investigated in the spectral region 1.0 to 4.7 eV at room temperature using polarized light. The electroreflectance structure in the region of the fundamental absorption edge and its polarization dependence are found to be in good agreement with the relative location of the valence bands earlier predicted theoretically. A great number of electroreflectance peaks has been observed in the spectral region 2.4 to 4.7 eV and interpreted by optical transitions at the I?, T, and N points of the Brillouin zone of the chalcopyrite lattice. The only transitions used were direct ones and responsible for the main structure in the optical spectra of sphalerite crystals. In addition, the fine structure of these optical transitions due to crystal field splitting has been included. npeHCTaBjIeHbI pe3yJIbTaTbI HCCJleAOBaHIIH CIIeIETpOB 3JIeHTPOOTPaHEeHHR MOHO-KpHCTaJIJIOB CdSnP, B IIOJIRpI130BaHHOM CBeTe B CIIeIFTpaJIbHOfi o6nac~H OT 1 ,o A 0 4,7 3B IIpH KOMHaTHOfi TeMIIepaType. CpTyHTypa CIIeKTpOB 3JIeKTpOOTpaHEeHIIR B o 6 n a c~~ OCHOBHOrO KpaR IIOrJIO~eHHR El ee IIOJIHpH3alJHOHHaR 3aBHCIIMOCTb IlOATBePAHJIU paHee TeOpeTHqeCKH IIpenCKa3aHHyIO CTPYKTYPY BaJleHTHOfi 30HbI. MHOHl eCTBO IIHHOB 3JIeHTpOOTpaHEeHUR B CIleHTpaJIbHOfi obnac~I1 OT 2,4 A0 4,7 3B XOpOluO HHTepIlpeTHpyeTCR OIITHqeCKUMH IIepeXOHaMH B TOqKaX r, T H N 3 0 H H EpHJIJIlO3Ha XaJlbKOIIUpHTa) 6blBIIIEIMH IlPRMbIMH H B C@aJIepHTe, IIpU YqeTe HX T O H H O~ CTPYICTYP~I BcneficTBm IipmTannmecKoro pacuenneHm, 0 6 y c n o~n e~-Horo ne@opMamiefi II HanmHeM HBYX COPTOB KaTHoHoB B pelue-me CdSnP,. 29

Thermoreflectance spectra and energy band structure of ZnGeP2 crystals

“…Following this model the peaks at higher energies are attributed only to optical transitions having been direct in sphalerite and responsible for the main structures El, Ei, and E, in the optical spectra of AI'IB" compounds. The richer structures in optical spectra of A1lBIVCY compounds are mainly caused by the splittings of the corresponding bands under the influence of the asymmetrical part of the crystal potential due 2, The notation of peaks is the same as for the other AIIBIVCT crystals [22] (the weak peak E, is absent in the thermoreflectance spectrum of ZnGePJ. .…”

“…The energies and pronounced polarizations of the thermoreflectance peaks El to and Ee to of ZnGeP, are listed in Table 1. The interpretation of thermoreflectance peaks a t higher energies has been done according to the model [22] based on energy band structure calculations and taking into account the changes of the band structure passing from the AIIIBV compound to its ternary analogue A1IBIVC:. Following this model the peaks at higher energies are attributed only to optical transitions having been direct in sphalerite and responsible for the main structures El, Ei, and E, in the optical spectra of AI'IB" compounds.…”

Assignment ofE1Transitions in II-IV-V2Chalcopyrite Crystals

“…As such effects may be even more important in predicting properties of "superheavy" nuclei, it is desirable that they be understood in the experimentally accessible regions of the periodic table. A recent Letter of McGowan et al 3 reported on such…”

“…Kavaliauskas et al 3 have proposed that these four transitions in CdSnP 2 are centered about the N point of the chalcopyrite Brillouin zone. Because of the ordering of the cations, the chalcopyrite Brillouin zone has one quarter of the volume of the zinc-blende Brillouin zone.…”

“…Kavaliauskas et at. 3 have further proposed that the two doublets in CdSnP 2 involve N x valence bands derived from InP valence bands mapped to the N point from two different L points. Kwan and Woolley 5 have assigned the second and third peaks in ZnSiAs 2 to the region of the chalcopyrite Brillouin zone corresponding to the A direction in zinc-blende.…”