Published in J. Appl. Phys. 89, 4815 (2001).
InGaAs/InP quantum well intermixing studied by cross-sectional
scanning tunneling microscopy
Huajie Chen,* R. M. Feenstra,* G. C. Aers,** P. J. Poole,**
R. L. Williams,** S. Charbonneau,** P. G. Piva,*** R. D. Goldberg,***
and I. V. Mitchell***
*Department of Physics, Carnegie Mellon University, Pittsburgh,
Pennsylvania 15213
**Institute for Microstructural Sciences,
National Research Council of Canada, Ottawa, K1A0R6, Canada
***Department of Physics and Astronomy, University of Western Ontario,
London N6A3K7, Canada
Abstract
Cross-sectional scanning tunneling microscopy (STM) is used to study
lattice matched InGaAs/InP quantum well (QW) intermixing induced by
ion implantation and thermal annealing. Different strain development
in QWs (determined by STM topography of elastic relaxation in
cross-sectionally cleaved samples) is found to be dependent
upon the range of the implanted ions relative to the QWs. It is found
that the quantum wells remain latticed matched to the barrier layers
after intermixing when ions are implanted through the multiple quantum
well (MQW) stack. A shallow implantation in which ions are implanted
into the cap layer above the MQW stack leads to tensilely strained
wells and compressively strained interfaces between wells and
barriers. The strain development in the latter case is attributed to
different degrees of interdiffusion on the group III and group V
sublattices. Finite element elastic computations are used to extract
the group V and group III interdiffusion length ratio, and results
using different diffusion models are compared. A preferred group V
interdiffusion in the case of shallow implantation is explained in
terms of faster diffusing P related defects compared to In related
defects. Images of as-grown QWs provide useful information about the
growth-technique related compositional fluctuations at the interfaces.
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