Infrared Transmission of Czochralski Germanium and Silicon
The current report demonstrates the temperature vs. transmission vs. resistivity relationship for the less explored IR wavelength range of 6 to 22 micrometers for silicon and 10 to 22 micrometers for germanium over the temperature range of -100 degrees C to 25 degrees C. These studies involve a wide range of resistivities. Material samples include n- type Si of 4000, 160, and 12 ohm-cm, and n-type Ge of 35, 2.5, and 0.5 ohm-cm. Silicon has useable transmission bands only between 1.2 and 8.5 micrometers , between 14 and 15.6 micrometers , and greater than 20 micrometers with best transmission occurring between 1.2 and 6.5 micrometers . Germanium has a useable transmission band between 2 and 17 micrometers with best transmission between 2 and 11.5 micrometers . The temperature dependence of IR transmission becomes more pronounced with increasing wavelength: 1.5 percent to 11.5 percent and 3 percent to 9.5 percent for silicon and germanium respectively over the temperature range of -100 degrees C to 25 degrees C. The 4000 ohm-cm Si sample exhibits significantly greater transmission at wavelengths of both 9.0 and 19.5 microns. The temperature dependence of lattice absorption is observed in germanium. This study builds a bridge between previously determined absorption mechanisms of the near and far IR ranges and may be used to develop the feasibility of silicon and germanium as optical windows or lenses within an extraterrestrial environment.
P. D. Ownby et al., "Infrared Transmission of Czochralski Germanium and Silicon," Proceedings of SPIE 4452, Inorganic Optical Materials III, 17 (2001: Nov. 2), SPIE -- The International Society for Optical Engineering, Aug 2001.
The definitive version is available at https://doi.org/10.1117/12.446889
Materials Science and Engineering
Article - Conference proceedings
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