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Picosecond imaging of photoexcited carriers in quantum wells: Anomalous lateral confinement at high densities

1988; American Physical Society; Volume: 38; Issue: 8 Linguagem: Inglês

10.1103/physrevb.38.5788

1095-3795

Leigh M. Smith, D. R. Wake, J. P. Wolfe, Dean H. Levi, M. V. Klein, John F. Klem, T. Henderson, H. Morkoç̌,

Terahertz technology and applications

We have measured the in-plane motion of photoexcited carriers in semiconductor quantum wells and have discovered several surprising results. The effective diffusivity of the carriers at densities below $n=2\ifmmode\times\else\texttimes\fi{}{10}^{11}$ ${\mathrm{cm}}^{\ensuremath{-}2}$ is found to depend upon the excitation level, possibly indicating defect-limited diffusion or phonon-wind effects. Above this density the spatial profiles exhibit two distinct components with widely differing diffusivities. We postulate that the slowly diffusing component represents carriers which are "thermally confined" to a phonon hot spot.