Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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Author: search.filters.author.Tarhan, EnverPublisher: search.filters.publisher.Springer

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  • Article
    Citation - WoS: 9
    Citation - Scopus: 7
    Epitaxial Characteristics of Mbe-Grown Znte Thin Films on Gaas (211)b Substrates
    (Springer, 2019) Özçeri, Elif; Tarhan, Enver
    Highly crystalline ZnTe thin films were grown on GaAs (211)B substrates by molecular beam epitaxy (MBE) for potential applications such as MCT detectors and optoelectronic devices. We investigated the effects of Te to Zn (VI/II) flux ratio on the quality of ZnTe films in terms of crystal orientation, elemental composition, surface roughness, and dislocation density. Atomic concentrations of Zn, Te, and oxygen complexes due to oxygen contamination on the film surfaces were analyzed by X-ray photoelectron spectroscopy. X-ray double crystal rocking curve full width half maximum (FWHM) of ZnTe (422) peak was observed as 233 arcseconds for a 1.66 mu m thick film, which indicates high crystallinity. Wet chemical etching was applied to the films to quantify the crystal quality by calculating etch pit densities (EPD) from scanning electron microscope images. A very low EPD value of 1.7 x 10(7) cm(-2) was measured. Additionally, the root mean square roughness values, obtained from atomic force microscopy topography images were in the range of 10-25 nm. These values were supported by FWHM values of red green blue color intensity histograms obtained from Nomarski Microscope images. The results of our analyses indicate that the VI/II flux ratios of 4 and 4.5 produce the best quality ZnTe films on GaAs (211)B substrates.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 10
    Effect of Annealing on the Density of Defects in Epitaxial Cdte (211)/Gaas
    (Springer, 2018) Bakali, Emine; Selamet, Yusuf; Tarhan, Enver
    CdTe thin films were grown on GaAs (211) wafers by molecular beam epitaxy as the buffer layer for HgCdTe infrared detector applications. We studied the effect of annealing on the density of dislocation of these CdTe thin films under varying annealing parameters such as annealing temperature, annealing duration, and number of cycles. Annealings were carried out using a homemade annealing reactor possessing a special heater element made of a Si wafer for rapid heating. The density of dislocations, which were made observable with a scanning electron microscope after etching with an Everson solution, were calculated by counting the number of dislocations per unit surface area, hence the term etch pit density (EPD). We were able to decrease EPD values by one order of magnitude after annealing. For example, the best EPD value after a 20-min annealing at 400°C was ∼ 2 × 107 cm−2 for a 1.63-μm CdTe thin film which was about 9.5 × 107 cm−2 before annealing. We also employed Raman scattering measurements to see the changes in the structural quality of the samples. From the Raman measurements, we were able to see improvements in the quality of our samples from the annealing by studying the ratio of 2LO/LO phonon mode Raman intensities. We also observed a clear decrease in the intensity of Te precipitations-related modes, indicating a decrease in the size and number of these precipitations.