Spectroscopic and microscopic investigation of MBE-grown CdTe (211)B epitaxial thin films on GaAs (211)B substrates
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CdTe epitaxial thin films, for use as a buffer layer for HgCdTe defectors, were grown on GaAs (211)B using the molecular beam epitaxy method. Wet chemical etching (Everson method) was applied to the epitaxial films using various concentrations and application times to quantify the crystal quality and dislocation density. Surface characterization of the epitaxial films was achieved using Atomic force microscopy and Scanning electron microscopy (SEM) before and after each treatment. The Energy Dispersive X-Ray apparatus of SEM was used to characterize the chemical composition. Untreated CdTe films show smooth surface characteristics with root mean square (RMS) roughnesses of 1.18–3.89 nm. The thicknesses of the CdTe layers formed were calculated via FTIR spectrometry and obtained by ex situ spectroscopic ellipsometry. Raman spectra were obtained for various temperatures. Etch pit densities (EPD) were measured, from which it could be seen that EPD changes between 1.7 × 108 and 9.2 × 108 cm−2 depending on the concentration of the Everson etch solution and treatment time. Structure, shape and depth of pits resulting from each etch pit implementation were also evaluated. Pit widths varying between 0.15 and 0.71 µm with heights varying between 2 and 80 nm were observed. RMS roughness was found to vary by anything from 1.56 to 26 nm.
KeywordsCdTe films CdTe buffer layer Etch pit density Raman spectroscopy Atomic force microscopy Scanning electron microscopy
This study was supported by the Gediz Project at Izmir Institute of Technology. The authors would like to thank all supporters for their assistance with the project. This paper is dedicated to the memory of Prof Yusuf Selamet, who sadly passed away in 2016. We are grateful to him for his guidance, endless support and giving us the chance to work with him. In addition, we would like to thank Elif Bilgilisoy for helping in etching CdTe epitaxial films and also Merve Karakaya for Spectroscopic Ellipsometry analysis. Use of facilities at the IZTECH Material Research Center for scanning electron microscopy is acknowledged.
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Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
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