Modified Bridgman assisted ZnTe crystal growth for THz device applications

• Published in: Journal of alloys and compounds Vol. 1001; p. 175176
• Main Authors: Vijayakumar, P., Tadka, S.N., Balaraju, K., Mahajan, Sandeep, Purushotham, Y., Chaudhary, A.K., Sarguna, R.M., Ganesamoorthy, S., Ratheesh, R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.10.2024
• Subjects: Bridgman technique; IR microscopy; Laue diffraction; THz spectroscopy; ZnTe crystal growth; THz spectroscopy; Bridgman technique; Laue diffraction; IR microscopy; ZnTe crystal growth
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2024.175176

Zinc Telluride (ZnTe) single crystals have enormous potential for generating and detecting broadband terahertz (THz) radiation, making them suitable for a wide range of applications in communication, defence security and biomedical applications. The quality and homogeneities of the crystal plays an important role in obtaining THz response. This paper elaborates on the steps involved in the crystal growth of ZnTe and the characterization technique utilized for the determination of quality of the grown crystal, identifications of defects and qualifications of THz signals. Single crystal was grown by the Bridgman technique in vacuum sealed carbon-coated quartz ampoule with excess tellurium (Zn:Te/3:7). To obtain maximum THz response, crystals were oriented along (110) direction using a Laue diffraction pattern and sliced accordingly. Three different crystals along the length (bottom-middle-top) of size ∼ 10 mm × 10 mm are taken for analysis. The crystallinity of ZnTe was confirmed with X-ray diffraction pattern and lattice parameters were obtained using Rietveld refinement. Raman analysis was carried out at three different regions of the grown crystal which revealed the presence of same high-intensity mode at 413 cm−1 in all the regions confirming the quality of the crystal. The EDS compositional analysis confirms the stoichiometry along the grown crystal length. Optical bandgap of 2.216 eV was measured by UV-Vis-NIR spectra and >55 % transmission was obtained across the grown crystal length. The size and distribution of Te inclusions were measured using IR microscopy. The crystals were subjected to terahertz investigation in the range of 0.1–4 THz using a time domain spectrometer. All the crystals exhibited negligible absorption coefficients in the 0.1–3.75 THz range, confirming the maximum transmission in the THz domain. The crystals also exhibit excellent electro-optic detection which is confirmed by signal-to-noise ratio in the measured range. [Display omitted] •ZnTe synthesis and crystal growth in single ampoule to reduce the process duration and avoid contamination.•Structural and compositional uniformity across the length of the grown crystal confirmed.•THz response across the grown ZnTe crystal confirms the suitability for imaging applications.