The synthesis of large-diameter ZnTe crystal for THz emitting and detection

A high-quality, large-size ZnTe ingot with the diameter of 60 mm and the length of 80 mm were prepared by the modified temperature gradient solvent method, where the Te rich solution acted as both solubility promoter and reactant. Using this method, the crystallization temperature was reduced from 1568 K to 1333 K, plus, the crystal defects could be reduced in some extent due to the lower zinc partial pressure. Few Te inclusions are found in the as-grown ZnTe crystal with the bulk factor less than 0.1%. X-ray diffraction (XRD), infrared transmission microscope, fourier transform infrared (FT-IR) spectrometer, ultraviolet-visible (UV-Vis) spectrophotometer were used to analyze the qualities and properties of the ZnTe crystals. The infrared transmittance over the wavenumber range from 500 to 4000 cm−1 is about 60% and the band gap is about 2.23 eV at the room temperature. The FWHM of the detection pulse with the THz time-domain spectroscopy (THz-TDS) is about 0.34 ps. Besides, both the radiation and detection pulse have a wide frequency distribution about 3 THz at the room temperature. These results strongly indicate that the high-quality ZnTe crystal synthesized by the temperature gradient solvent method is superior for THz device applications.