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In0.2Ga0.8As/GaAs interface revealed by an AlAs marker layer

Authors :: Glaisher, R. W.
Cockayne, D. J. H.
Usher, B. F.
Source :: Applied Physics A: Materials Science & Processing; November 1993, Vol. 57 Issue: 5 p401-405, 5p
Publication Year :: 1993
Abstract: A detailed analysis of the microstructure of layered semiconductor heterostructures is only possible if the interface between the various layers can be accurately located. Microstructural features whose characterisation is dependent on the location of the interface include the planarity and width of the layers, the composition profile and the geometry of misfit dislocations (in the particular case of lattice mismatched heterostructures). We report on an investigation to image, at high resolution in the transmission electron microscope, the interface in an In<subscript>0.2</subscript>Ga<subscript>0.8</subscript>As/GaAs structure grown by molecular beam epitaxy. The difficulty in locating the interface, due to similarity in electron optical behaviour of GaAs and In<subscript>0.2</subscript>Ga<subscript>0.8</subscript>As when imaged in a <110> direction, was overcome by incorporating into the structure a “marker layer” of AlAs two unit cells thick (11.4 Å in total) between the GaAs and the In<subscript>0.2</subscript>Ga<subscript>0.8</subscript>As layers. Lattice fringe images of an In<subscript>0.2</subscript>Ga<subscript>0.8</subscript>As/AlAs/GaAs structure are presented which show, at near atomic resolution, the location of the misfit dislocations relative to the In<subscript>0.2</subscript>Ga<subscript>0.8</subscript>As/GaAs interface.