Point defects, localized vibrational modes, and free-carrier absorption of Al-doped CdTe
- 1 February 1976
- journal article
- research article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 47 (2), 565-572
- https://doi.org/10.1063/1.322661
Abstract
Infrared absorption bands attributable to the localized vibrational modes for several Al‐related point defects have been observed for CdTe. The proposed defects, their point‐group symmetries, and the vibrational frequencies at 80 °K in cm−1 are as follows: AlCd, Td, 299; AlCd‐VCd, Cs, 282,287,326; AlCd‐SbTe, C3v, 279,334; AlCd‐CuCd, Cs, 291,294, 310; AlCd‐AgTe or AlCd‐Agi, C3v, 293,314; AlCd‐AuTe or AlCd‐Aui, C3v, 292,313; and possibly AlCd‐AuCd, Cs, 288 (two unresolved bands), 326. The Al and Sb were introduced during crystal gwoth and the Cu, Ag, and Au by saturation diffusions. Annealing of CdTe:Al with [Al]∼1×1019 cm−3 in unsaturated Cd‐rich atmospheres produced electron concentrations of 2×1018 and 2×1017 cm−3. Free‐carrier absorption measurements at 298 and 80 °K give a nearly temperature‐independent absorption coefficient with a frequency dependence of ω−3 after ther higher carrier density anneal with ω−4 for the lower carrier concentration. The free‐carrier absorption results are compared with previously reported data and also recent theoretical calculations for CdTe which predict, under appropriate conditions, α∼ω−3 for the polar optical mode scattering and α∼ω−4 for ionized impurity scattering.Keywords
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