Compensating and recombination centers in CdTe and CdSe
Final Report Abstract
The main results of the project can be summarized as follows. • IR absorption spectroscopy and first principle calculations have been applied to identify the substitutional sulfur defect, SSe, in wurtzite single-crystalline CdSe. The measurements performed on nominally undoped as well as 34S-implanted samples provided conclusive evidence that SSe results in two IR absorption lines at 270.6 and 271.4 cm^-1 assigned to stretch vibrational modes transformed under the nondegenerate Ai and the twofold degenerate E states of the C3v point group, respectively. • Temperature and polarization sensitive IR absorption spectroscopy identified substitutional oxygen at cation sites in cubic CdTe and wurtzite CdSe. The line at 349.8 cm^-1 in CdTe was associated with a vibrational mode of Oye- In CdSe, Ose gives rise to a vibrational mode doublet, whereby the lower and upper frequency modes at 370.6 and 372.5 cm-1 are due to the and E representations of the C3v point group, respectively. • The earlier interpretation of the double IR absorption feature at 1097 and 1108 cm^-1 in CdTe as asymmetric stretching vibrations of an SO*2 molecule was revised. A combined IR absorption and first principles theory study revealed that a sulfate ion located on the cation vacancy sites, SO*4, is the most plausible model for the complex. • IR absorption spectroscopy and first-principles theory were employed to probe a sulfur-oxygen complex in CdSe characterized by stretch vibrational modes at 1094, 1107, and 1126 cm^-1. It was shown that, similar to CdTe, the sulfate ion occupying anion vacancy sites, SO*4, is the best model complying with all experimental and theoretical findings, whereby the local symmetry of SO*4 drops from C3v in cubic CdTe to Cs in the hexagonal wurtzite CdSe.
Publications
- Substitutional Sulfur in CdSe: Localized Vibrational Modes," Phys. Status Solidi B 257, p. 2000204, 2020
F. Herklotz, E. V. Lavrov, and V. V. Melnikov
(See online at https://doi.org/10.1002/pssb.202000204) - SO*4 complex in CdTe: Infrared absorption spectroscopy and first-principles calculations, Phys. Rev. B 104, p. 035204, 2021
F. Herklotz, E. V. Lavrov, and V. V. Melnikov
(See online at https://doi.org/10.1103/PhysRevB.104.035204) - Vibrational Signatures of Substitutional Oxygen in CdTe and CdSe, Phys. Status Solidi B 258, p. 2100203, 2021
F. Herklotz, S. Tiede, and E. V. Lavrov
(See online at https://doi.org/10.1002/pssb.202100203) - SO4 in Cadmium Chalcogenides: CdSe versus CdTe, Phys. Status Solidi B 259, p. 2200029, 2022
F. Herklotz, E. V. Lavrov, and V. V. Melnikov
(See online at https://doi.org/10.1002/pssb.202200029)
