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Journal of Physical Studies 19(4), Article 4702 [5 pages] (2015)
DOI: https://doi.org/10.30970/jps.19.4702 STRUCTURAL AND PHOTOLUMINESCENCE PROPERTIES OF MONOCRYSTALS CdTe:VA. Kuryk, N. Safriuk, S. Budzulyak, V. Ermakov, V. Kladko, D. Korbutyak
V. E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, |
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A comprehensive study of structural and photoluminescent properties of single crystals of CdTe:V samples has been made. Single crystal ingots were grown using the vertical Bridgman method with a temperature gradient of 25$\circ$\,C/cm. An estimated concentration of vanadium impurity in the melt was 10$^{19}$cm$^{-3}$. Free carrier concentration was $(4-7)\times10^6$\,cm$^{-3}$ at room temperature. Single crystals with the desired electrophysical characteristics have been obtained when free volume above the melt was approximately the same as the melt volume. The ingots with a diameter of 15 mm and a length of 80 mm have been obtained. To study structural and photoluminescent properties of CdTe:V the samples were cut from the top, middle, and bottom parts of the ingot. To obtain information on the type, sizes, and concentration of structural defects in the CdTe:V samples we have used the method of measuring the half-widths of the reflection curves in X-ray diffraction and an analysis of the diffusive scattering of X-rays for symmetric (220)] reflexes. The parameters of the crystal lattice have been obtained from the w-scans of the (220) reflex. The integral characteristic of structural perfection is associated with the half-width of the w-scans. The smallest half-width of w-scans has been found for the samples from ingot beginning, which indicate their structural perfection. We have found that defects of both vacancy and interstitial types are present in CdTe:V samples and the volume of large vacancy defects exceeds that of node defects. The analysis of the axial distribution of radiation in the exciton region is indicating the change in the impurity-defect structure along the growth direction, the change being caused by the technological features of the growth. A growth in cadmium concentration has been found along the direction of crystal growth, which brings about the formation of the donor-acceptor complexes with participation of shallow donors; as a result the concentration of shallow donors falls along this direction. We have found that the most structurally perfect sample is obtained from the bottom of the crystal.
PACS number(s): 78.55.Et, 81.10.Fq