Relevance of Thermal Mismatch in Large-Area Composite Substrates for HgCdTe Heteroepitaxy |
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Authors: | RN Jacobs LA Almeida J Markunas J Pellegrino M Groenert M Jaime-Vasquez N Mahadik C Andrews SB Qadri T Lee M Kim |
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Affiliation: | (1) U.S. Army RDECOM, CERDEC Night Vision and Electronic Sensors Directorate, Fort Belvoir, VA 22060, USA;(2) U.S. Naval Research Laboratory, Washington, DC 20375, USA;(3) Department of Electrical Engineering, University of Texas, Dallas, TX 75083, USA |
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Abstract: | It is well known that the large lattice mismatch (>14%) associated with CdTe/Si, CdTe/Ge, and CdTe/GaAs composite substrates,
is a great contributor to large dislocation densities and other defects that limit the performance of HgCdTe-based infrared
detectors. Though thermal expansion mismatch is another possible contributor to material defects, little work has been done
towards documenting and understanding its effects in these systems. Here, we perform studies to determine the relative contributions
of lattice and thermal mismatch to CdTe film characteristics, including dislocation density and residual stress. Unannealed
and thermally cycled films are characterized using x-ray diffraction, defect decoration, and Nomarski and transmission electron
microscopy. For CdTe/Si, the residual stress is consistently observed to be tensile, while for CdTe/Ge and CdTe/GaAs, a compressive
residual film stress is measured. We show based on theoretically predicted stress levels that the experimental measurements
imply the dominance of thermal mismatch in the residual stress characteristics. |
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Keywords: | Residual film stress thermal mismatch HgCdTe CdTe buffer mismatched heteroepitaxy silicon germanium gallium arsenide |
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