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Journal of Physical Studies 6(3), 347–353 (2002)
DOI: https://doi.org/10.30970/jps.06.347 THE INFLUENCE OF γ-IRRADIATION ON CHARACTERISTICS OF EDGE PHOTOLUMINESCENCE IN UNDOPED CdTeN. D. Vakhnyak1, S. G. Krylyuk2, Yu. V. Kryuchenko2, I. M. Kupchak2
1Yu. Fed'kovych Chernivtsi National University, |
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We have studied the effect of $γ$-irradiation with different doses ($D=1\div300$ kGy) on the edge ($E=1.50-1.57$ eV) low-temperature photoluminescence (PL) of undoped CdTe crystals. Numerical fitting of experimental edge PL spectrum at $D<10$ kGy gives evidence for this spectrum formation by two closely-spaced bands. One of them, the (e-A)-band, is attributed to the recombination of a free electron with a hole localized at an acceptor center, while the other, the (D-A)-band, is due to the donor-acceptor recombination. $γ$-irradiation of CdTe crystals with relatively small doses leads to the (D-A)-band quenching and its complete disappearance at $D≈$10 kGy. We believe it occurs due to the destruction of the corresponding donor centers at such a treatment. Contrary to the (D-A) recombination, the relative intensity of the (e-A)-band $I_{\rm PL}^{(e,A)}/I_{\rm PL}^{(A^0,X)}$ (where $I_{\rm PL}^{(A^0,X)}$ is the intensity of the $(A^0,X)$ line of excitons bound to neutral acceptors) increases dramatically at $D>10$ kGy due to the effective generation of Cd vacancies which are responsible for acceptor centers formation. From the energy shift of the (D-A)-band we have evaluated the mean distance $R≈ 12$ nm between donor and acceptor in D-A pairs. Theoretical calculations of the Huang-Rhys factor $S_{\rm DA}$ as a function of the distance $R$ for D-A recombination have been made as well. The results of the calculations have been compared with the values $S_{\rm DA}^{\exp}$ of the Huang-Rhys factor obtained from the experiment.
PACS number(s): 78.55.Et; 78.55.-m