OPTICAL SPECTROSCOPY OF HIGH –RESISTTNCE CdTe SINGLE CRYSTALS

Recently, more and more attention has been paid to the technology of growing high-resistance CdTe crystals. The development of the technology is based on the control of the synthesis processes, the determination of the defective structure and its effect on the physical properties of the material. The conditions for obtaining the material determine the composition and distribution of point defects, which significantly affect the electronic processes in the material. Cadmium telluride is used to make uncooled gamma radiation detectors. CdTe doped with chlorine turned out to be especially promising in this regard. One of the main problems when using the A2B6 semiconductor compounds as the basic material of optoelectronics is obtaining a homogeneous material. This paper presents the experimental results of the study of optical reflection and transmission spectra in the spectral range 800 nm - 1100 nm, optical reflection and transmission spectra in the spectral range (1.4 – 25) 10-6 m of high-resistance CdTe single crystals of (111) orientation with with specific resistance ρ = 2.109 Om∙cm -5∙109 Om∙cm, doped with chlorine. Optical spectra of reflection and transmission in the region of the fundamental optical transition E0 of CdTe (111) single crystals (spectral range 800 nm - 1100 nm) were measured using a diffraction grating monochromator MDR-23. The resolution of the MDR-23 diffraction grating monochromator is 2.10-4 eV. Registration of optical spectra of reflection and transmission in the spectral range (1.4 - 25) 10-6 m was carried out on a PerkinElmer SpectrumBXII infrared Fourier spectrometer. The measurement error of the optical spectra is equal to 2 cm-1. The measurements were carried out at room temperature. It was determined that the energy of the fundamental optical transition E0 of CdTe single crystals doped with chlorine of the (111) orientation with a resistivity ρ = 2 .109Om∙cm - 5∙109Om∙cm at T = 300 K is equal to 1.44 eV. The energy relaxation time of free charge carriers τ and the effective optical mobility of free charge carriers for high-resistance single crystals of CdTe (111) were estimated. It is shown that the studied crystals have a high (detector) quality, which is decisive for the manufacture of highly sensitive and high resolution sensors of ionizing radiation.