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KMID : 1159320160180040447
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Korean Journal of Vision Science
2016 Volume.18 No. 4 p.447 ~ p.454
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The properties of Thermodynamic Functions and Photoluminescence in ZnAl2Se3.6S0.4 Single Crystal
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Park Kwang-Ho
Hyun Seung-Cheol
Kim Duck-Tae
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Abstract
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Purpose: As a study on solid solution compound of the Ⅱ-Ⅲ2-Ⅵ4 type semiconductor, we investigated the structure and photoluminescence properties of ZnAl2Se3.6S0.4 solid solution and from these properties we calculated the temperature dependence of optical band gap and estimated fundamental thermodynamic functions.
Methods: ZnAl2Se3.6S0.4 single crystal was grown by CTR method using iodine as a transporting material. We positioned the ampoule in the middle of the two zones furnace, we maintained 7 days at 950 ℃ in the starting site and 850 ℃ in the growing site, respectively. To obtain the temperature dependence of the optical energy band gap at fundamental absorption edge, optical absortion spectrum was measured by UV-VIS-NIR spectrophotometer equipped with cryogenic system. Photoluminescence property of the sample located at the finger of cryogenic system was examined by the measurement system equipped with 325㎚ He-Ne laser, double-grating monochromator, data-mate control system, cryogenic system and PM tube.
Results and Consideration: To obtain the temperature dependences of the energy band gaps, we examined the optical absorption spectra in the wavelength range 320 ? 420㎚ around the fundamental absorption edge and in the temperature range 13 ? 289K. The temperature dependences of the energy band gaps was well fitted with Varshni equation. We could deduct the thermodynamic functions from the temperature dependent optical energy band gap(Eg). Also, in the photoluminescence spectrum measured at 13K, we could observe a wide-strong peak at 427㎚(2.904eV) and weak blue one at 468㎚ (2.648eV), respectively.
Conclusions: The ZnAl2Se3.6S0.4 single crystal had defect chalcopyrite structure and the lattice constants were a= 5.5563Å, c= 10.8324Å, respectively. The distortion factor of this lattice constants was 0.0504. From the temperature dependences of the energy band gaps, we obtained Eg(0)=3.538(eV), α=2.02×10-3(eV/K), β=502.19(K), respectively. Also, we could deduct the thermodynamic functions from the measured-temperature dependent optical energy band gap(Eg). And, at 13K, we could observe a wide-strong blue photoluminescence peak at 427㎚(2.904eV) and weak blue one at 468㎚ (2.648eV), respectively. These two photoluminescence peaks was explained by the recombination mechanism between two donor levels(SD1, DD1) and one acceptor level(DA1).
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KEYWORD
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Solid solution, donor level, acceptor level, Entropy, SCV, Heat capacity, CCV, Enthalpy, HCV
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