STUDY OF THE DIFFUSION LENGTH OF NONEQUILIBRIUM CHARGE CARRIERS IN CADMIUM TELLURIDE BASE LAYERS

Thin film samples of cadmium telluride were obtained using thermal vacuum evaporation to study the diffusion length of minority charge carriers. Initial state analysis was conducted through X-ray structural studies of cadmium telluride condensed on glass substrates. The analysis revealed two diffraction reflections corresponding to the crystallographic planes (111) and (333). Calculations showed that the sizes of coherent scattering regions were 93 nm and 56 nm, while microstrain values were determined as 11.6×10−3 and 4.8×10−3, respectively, for these planes. Electron diffraction studies identified the zone axis of the formed film structures as [110]. Additionally, twinning and forming a layered substructure within the cadmium telluride thin films were observed. Microscopic surface studies provided insights into the surface relief, measured at approximately 130 nm, and the polycrystalline grain size, determined to be 1 micrometer. The method of spectral dependence of small-signal surface photovoltage was employed to investigate the electrophysical properties of cadmium telluride thin films. The diffusion length of minority charge carriers was calculated to be 0.45 micrometers, which is half the size of the grain dimensions. Furthermore, the transmittance coefficient of cadmium telluride was examined in the wavelength range of 800–900 nm. The optical bandgap energy was 1.4 eV, slightly lower than the 1.5 eV observed for monocrystalline cadmium telluride. In conclusion, cadmium telluride film structures produced by thermal vacuum evaporation exhibit electrophysical and electrical parameters inferior to monocrystalline cadmium telluride. These characteristics, particularly the low diffusion length of minority carriers and short electrical signal decay times make such film structures suitable for use in devices requiring long-term stability under the influence of time, extreme temperatures, electric fields, and radiation.