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Schematic diagram of GaAs pn junction with ErAs nanoparticles and of scanning capacitance measurement geometry and electrical connections.
(Color online) AFM surface topograph and SCM images for applied dc bias voltages ranging from −2.0 V to 0 V. SCM images obtained from identical areas are indicated by the brackets immediately to the left of the images. The AFM topograph was obtained simultaneously with the SCM image at 0 V. The centers of rectangles and circles indicate locations in each image corresponding to high and low subsurface ErAs content, respectively. The bottom SCM images were taken from a GaAs-only reference sample at −2.0 V and 0 V. All SCM images are shown using the same signal-level scale.
(Color online) (a) Simulated values for −dC/dV as a function of local subsurface ErAs content. (b) SCM signal levels extracted from the images shown in Fig. 2. (c) Energy band diagrams for the GaAs pn junction with ErAs nanoparticle fractional coverages of 60% (left) and 10% (right), under applied dc voltages of −0.5 V, 0.0 V, and +0.5 V.
(Color online) (a) Simulated distributions of ErAs coverage (dark areas) at the GaAs pn junction obtained by random placement of ErAs nanoparticles with radii of 4 nm, 6 nm, 8 nm, and 10 nm. For each distribution, the average fractional surface coverage is fixed at ∼0.28. (b) Normalized distributions of ErAs coverage fraction, averaged over 40 nm × 40 nm areas, for simulated distributions of ErAs nanoparticles with radii of 4-10 nm, and as extracted from SCM images obtained at bias voltages from −2.0 V to 0.0 V.
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