Sarugaku, Yuki; Kaji, Sayumi; Ikeda, Yuji
; Kobayashi, Naoto; Sukegawa, Takashi; Nakagawa, Takao; Kataza, Hirokazu; Kondo, Sohei; Yasui, Chikako; Nakanishi, Kenshi; Kawakita, Hideyo
2017, Journal of Electronic Materials
We report measurement of the internal attenuation coefficient, α_att, of a bulk high-resistivity cadmium zinc telluride (CdZnTe) single crystal at wavelength, λ = 0.84-26 μm, to the unprecedentedly low level of α_att〜0.001 cm^-1. This measurement reveals the spectral behavior for small attenuation in the infrared transparent region between the electronic and lattice absorptions. This result is essential for application of CdZnTe as an infrared transmitting material. Comparing the attenuation spectrum with model spectra obtained on the basis of Mie theory, we find that sub-micrometer-sized Te particles (inclusions) with a number density of approximately 10^7.5-9 cm^-3 are the principal source of the small attenuation observed at λ = 0.9-13 μm. In addition, we determine α _att = (7.7 ± 1.9) × 10^-4 cm^-1 at λ = 10.6 μm, which is valuable for CO_2 laser applications. Higher transparency can be achieved by reducing the number of inclusions rather than the number of precipitates. This study also demonstrates that high-accuracy measurement of CdZnTe infrared transmittance is a useful approach to investigating the number density of sub-micrometer-sized Te particles that cannot be identified via infrared microscopy.