Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - WoS: 4Citation - Scopus: 5Identifying Threading Dislocations in Cdte Films by Reciprocal Space Mapping and Defect Decoration Etching(American Institute of Physics, 2018) Polat, Mustafa; Bilgilisoy, Elif; Arı, Ozan; Öztürk, Orhan; Selamet, YusufWe study threading dislocation (TD) density of high-quality cadmium telluride (CdTe) layers grown on a (211) oriented GaAs substrate by molecular beam epitaxy. High-resolution X-ray diffraction was performed to calculate the density of screw-type TDs by measuring the broadening of the asymmetrical (511) Bragg reflections of CdTe epilayers. In addition, total TD densities were determined by the Everson-etching method and were compared with screw TDs. Our results show that the total TD densities in CdTe films were dominated by those with screw character. The screw component TDs are estimated to account for more than 90% of the total TD density. CdTe layers grown at a thickness of less than 3.0 μm typically exhibit the screw TD densities in the 106 cm-2 and 107 cm-2 range. It can be noted that as the nucleation temperature increases, i.e., ≥222 °C, both the area density of TDs with the screw component of the CdTe films and the total TD density are roughly four times larger than those of the epilayer grown at the nucleation temperature of 215 °C. Furthermore, we discuss the influence of the II/VI flux ratio on the density of threading dislocations. The contribution of screw TDs to the total TD density showed a significant decrease in roughly 30% in the case of a high II/VI flux ratio. We further examine the reciprocal space maps in the vicinity of the (422) reflections.Article Citation - WoS: 3Citation - Scopus: 3Growth and Characterization of Cdte Absorbers on Gaas by Mbe for High Concentration Pv Solar Cells(John Wiley and Sons Inc., 2015) Arı, Ozan; Polat, Mustafa; Karakaya, Merve; Selamet, YusufCdTe based II-VI absorbers are promising candidates for high concentration PV solar cells with an ideal band gap for AM1.5 solar radiation. In this study, we propose single crystal CdTe absorbers grown on GaAs substrates with a molecular beam epitaxy (MBE) which is a clean deposition technology. We show that high quality CdTe absorber layers can be grown with full width half maximum of X-ray diffraction rocking curves (XRD RC) as low as 227 arc-seconds with 0.5% thickness uniformity that a 2 μm layer is capable of absorbing 99% of AM1.5 solar radiation. Bandgap of the CdTe absorber is found as 1.483 eV from spetroscopic ellipsometry (SE) measurements. Also, high absorption coefficient is calculated from the results, which is ∼5 x 105cm-1 in solar radiation spectrum.