Visualizing period fluctuations in strained-layer superlattices with scanning tunneling microscopy

K. Kanedy, F. Lopez, M. R. Wood, Claire F. Gmachl, M. Weimer, J. F. Klem, S. D. Hawkins, E. A. Shaner, J. K. Kim

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3 Scopus citations

Abstract

We show how cross-sectional scanning tunneling microscopy (STM) may be used to accurately map the period fluctuations throughout epitaxial, strained-layer superlattices based on the InAs/InAsSb and InGaAs/InAlAs material systems. The concept, analogous to Bragg's law in high-resolution x-ray diffraction, relies on an analysis of the [001]-convolved reciprocal-space satellite peaks obtained from discrete Fourier transforms of individual STM images. Properly implemented, the technique enables local period measurements that reliably discriminate vertical fluctuations localized to within ∼5 superlattice repeats along the [001] growth direction and orthogonal, lateral fluctuations localized to within ∼40 nm along <110> directions in the growth plane. While not as accurate as x-ray, the inherent, single-image measurement error associated with the method may be made as small as 0.1%, allowing the vertical or lateral period fluctuations contributing to inhomogeneous energy broadening and carrier localization in these structures to be pinpointed and quantified. The direct visualization of unexpectedly large, lateral period fluctuations on nanometer length scales in both strain-balanced systems supports a common understanding in terms of correlated interface roughness.

Original languageEnglish (US)
Article number042105
JournalApplied Physics Letters
Volume112
Issue number4
DOIs
StatePublished - Jan 22 2018

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

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    Kanedy, K., Lopez, F., Wood, M. R., Gmachl, C. F., Weimer, M., Klem, J. F., Hawkins, S. D., Shaner, E. A., & Kim, J. K. (2018). Visualizing period fluctuations in strained-layer superlattices with scanning tunneling microscopy. Applied Physics Letters, 112(4), [042105]. https://doi.org/10.1063/1.5008865