Scanning tunneling microscopy of lnAs/GaSb superlattices: Subbands, interface roughness, and interface asymmetry

Creators: Feenstra, R. M.; Collins, D. A.; Ting, D. Z.-Y.; Wang, M. W.; McGill, T. C.

Abstract

Scanning tunneling microscopy and spectroscopy is used to characterize InAs/GaSb superlattices, grown by molecular-beam epitaxy. Roughness at the interfaces between InAs and GaSb layers is directly observed in the images, and a quantitative spectrum of this roughness is obtained. Electron subbands in the InAs layers are resolved in spectroscopy. Asymmetry between the interfaces of InAs grown on GaSb compared with GaSb grown on In As is seen in voltage-dependent imaging. Detailed spectroscopic study of the interfaces reveals some subtle differences between the two in terms of their valence-band onsets and conduction-band state density. These differences are interpreted in a model in which the GaSb on InAs interface has an abrupt InSb-like structure, but at the InAs on GaSb interface some Sb grading occurs into the InAs overlayer.

Additional Information

© 1994 American Vacuum Society. Received 25 January 1994; accepted 12 March 1994. The authors gratefully acknowledge H. Munekata for providing us with some lnAs wafers. This work was supported in part by the Advanced Research Projects Agency under Contract No. N00014-93-1-0881, and by the Air Force Office of Scientific Research under Contract No. F49620-93-1-0258.

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