X-ray Pole figure analysis for orienting TGSM grown bulk ZnTe crystal for Terahertz device applications

ZnTe crystal is an electro-optical crystal which is extensively utilized for Terahertz generation and detection in various spectroscopic, surveillance and defence applications. Precise orientation of ZnTe bulk crystal along (110) is very important for obtaining maximum terahertz response from ZnTe crystal. This paper reports growth of ZnTe crystal by temperature gradient solvent method (TGSM) at controlled low temperature similar to 1060 degrees C with main thrust on the use of X-ray Pole figure analysis to precisely orient the grown crystal along (110) orientation. The paper elaborates various steps in X-ray Pole figure technique to obtain precise orientation corrections in the form of crystal tilt and rotation values for the unoriented cut wafer providing adequate explanation on the interpretation and analysis of X-ray Pole figure data. Required (110) orientation of the oriented cut ZnTe crystal wafer is ascertained by X-ray pole figure and X-ray diffraction analysis. Both unoriented and (110) oriented ZnTe crystal wafers are analysed by Resonant Raman spectroscopy to study the effect of precise orientation on Raman scattering. Intensity of longitudinal optic multiphonon peaks in the resonant Raman spectra are enhanced in the (110) oriented ZnTe wafer. Finally, terahertz spectroscopy of (110) ZnTe is performed to evaluate the terahertz response of fabricated (110) ZnTe substrates which shows a high transmittance (similar to 70%) in the terahertz region and very strong electro-optic terahertz detection which is attributed to controlled low-temperature growth and precise orientation cutting along direction of ZnTe crystal.

Automated summary

This paper presents the growth of ZnTe crystal by the temperature gradient solvent method and the use of X-ray pole figure analysis to precisely orient the crystal along the (110) direction. The effect of orientation on Raman scattering and the terahertz response of (110) ZnTe substrates are studied. The results show enhanced multiphonon peaks in the resonant Raman spectra and high transmittance in the terahertz region for the (110) oriented ZnTe crystals.