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Preparing Perfect Single Crystal Films

IP.com Disclosure Number: IPCOM000088157D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Matthews, JW: AUTHOR

Abstract

Mader and Matthews describe in U. S. Patent 3,788,890 a method for making perfect (dislocation free) single crystals. The method made use of the elastic (misfit) stresses generated when one crystal is grown epitaxially on another to drive dislocations towards, and finally out of, the edge of the sample. Illustratively, the process has been found to operate satisfactorily for samples in the nature of III-V compounds like GaAs and GaP. Dislocation motion in GaAs films (oriented with (001) parallel to their plane) is unsymmetric. Slip-on planes that meet the (001) surface along [110] proceeds more or less easily than slip-on planes that meet the (001) surface along [010]. This asymmetry plays an important and helpful role in the removal of dislocations.

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Preparing Perfect Single Crystal Films

Mader and Matthews describe in U. S. Patent 3,788,890 a method for making perfect (dislocation free) single crystals. The method made use of the elastic (misfit) stresses generated when one crystal is grown epitaxially on another to drive dislocations towards, and finally out of, the edge of the sample. Illustratively, the process has been found to operate satisfactorily for samples in the nature of III-V compounds like GaAs and GaP. Dislocation motion in GaAs films (oriented with (001) parallel to their plane) is unsymmetric. Slip-on planes that meet the (001) surface along [110] proceeds more or less easily than slip-on planes that meet the (001) surface along [010]. This asymmetry plays an important and helpful role in the removal of dislocations. It prevents interaction between dislocations that glide on the pair of {111} planes that meet the sample surface along [110] with those that glide on planes that meet the surface along [110]. Extension of the Mader-Matthews method to crystals that are more symmetric than III-V compounds would benefit from the artificial introduction of an asymmetry similar to that found in III-V's. How such an asymmetry can be introduced is described herein. Its introduction extends the method described by Mader-Matthews to in many materials including Si, Ge, and face-centered-cubic metals.

A situation is created artificially (which exists fortuitously in III-V compounds) that leads to effective removal of threading dislocations. Before...