OPTICAL ABSORPTION OF FE2+ IN CDTE IN NEAR AND FAR INFRARED

The optical-absorption spectrum of Fe2+ 3d6 impurities in CdTe crystals has been measured over the wave-number range from 10 to 120 cm-1 in the far infrared at 4.2 and 20°K, and from 2000 to 13 000 cm-1 in the near infrared at 2, 14, and 300°K. Transitions between the five spin-orbit levels of the E5 ground state have been seen in the far infrared, while transitions from E5 to the T25 and possibly higher states have been seen in the near infrared. The far-infrared results give the energies for two of the E5 levels as Γ1=0 and Γ4=18.6 cm-1, and two unspecified lines at ν̄=66.7 and 73.2 cm-1. These results also give phonon energies at several critical points in the Brillouin zone as TA(L)=36 cm-1, TA(X)=46 cm-1, LA(L)=104.5 cm-1. The Γ4 level of E5 has been found to split in a magnetic field with g=1.02. The magnetic susceptibility of Fe2+-doped CdTe has been measured from 4 to 300°K, and the results agree with predictions based on the calculated level positions of the E5 state in an applied magnetic field. An appendix is presented in which the theory of the splitting of the D5 free-ion state in the tetrahedral crystal field is given, and the resultant energies and wave functions of the individual spin-orbit levels are tabulated. © 1969 The American Physical Society.