Characterization of cross-hatch morphology of MBE (211) HgCdTe |
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Authors: | M. Martinka L. A. Almeida J. D. Benson J. H. Dinan |
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Affiliation: | (1) U.S. Army CECOM Night Vision & Electronic Sensors Directorate, 10215 Burbeck Road, 22060-5677 Ft. Belvoir, VA |
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Abstract: | We present the results of a detailed study of the nature and origin of cross-hatch patterns commonly observed on (211) HgCdTe epilayers deposited by molecular beam epitaxy. Cross-hatch patterns were examined using x-ray topography as well as Nomarski, interferometric, and atomic force microscopies. Cross-hatch patterns were generally comprised of three sets of lines, parallel to the [231],, [213], and [011] directions. The lines parallel to the [011] direction exhibited distinct properties compared to the two sets of lines parallel to [231] and [213]. Under growth conditions characterized by excessive Hg flux (low temperature), lines parallel to [011] were periodic and tended to dominate the cross-hatch pattern. In some cases, bands of dislocations, 10–100 m in width, formed parallel to [011]. Under optimized growth conditions, on very closely lattice-matched substrates, (dislocation densities <105 cm−2) lines parallel to [011] vanished entirely, and lines parallel to [231] and [213] became sparse. The remaining lines were typically fragments terminated by either a single dislocation, a cluster of dislocations (micro-void), or the wafer's edge. The density of these line fragments tended to decrease as the dislocation density decreased. Under the best growth conditions on very closely lattice-matched substrates we have achieved dislocation densities of 5 104 cm−2, which is comparable to the dislocation density of the CdZnTe substrate. |
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Keywords: | Cross-hatch HgCdTe CdZnTe lattice-mismatch defects |
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