Comparison of In1−xTlx Sb and Hg1−x Cdx Te as long wavelength infrared materials
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Cohesive energies, elastic constants, band structures, and phase diagram are calculated to evaluate the In1−xTlxSb alloy (ITA) as a long-wavelength infrared (LWIR) material compared to Hg1−xCdxTe (MCT). To obtain a 0.1 eV gap at zero temperature, the x value for ITA is estimated to be x=0.083 as compared to x=0.222 for MCT. At this gap, ITA is more robust than MCT because the cohesive energies order as InSb>TlSb>CdTe>HgTe, and ITA has the stronger bonding InSb as the majority component. Although TlSb is found to favor the CsCl structure, ITA is a stable alloy in the zincblende structure for low x values. However, our phase diagram indicates that it is difficult to grow the 0.1 eV gap ITA from the melt, because above the eutectic the liquidus curve is flat, and the solidus drops rapidly. Moreover, the width of the stable concentration range of the zincblende solid phase shrinks at low temperatures due to the presence of the CsCl structure.
Key wordsElastic constants InTlSb HgCdTe long-wavelength infrared materials phase diagram
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