Schematic representation of the MBE-grown QW structure.
HAADF-STEM images showing brighter -contrast for the individual InGaAs marker layers. Atomic resolution HAADF-STEM image (right) reveals almost atomically abrupt heteroepitaxial interfaces.
RBS spectrum for the QW structure, acquired using a 9 MeV beam under normal incidence and 170° backscattering angle. Inset shows a close-up of the six individually resolved InGaAs marker layers (linear scale).
SIMS depth profiles for selected positive ion species representing the GaAs matrix species and their respective O-cluster ions upon bombardment for different ion impact energies. The vertical arrow (left panel; 5 keV only) indicates the start of backfilling .
SIMS (top) and (bottom) ion intensity ratios as a function of apparent depth upon ion beam sputtering at different ion impact energies.
(a) Normalized -profiles (Atomika 4500) around the position of the second (104 Å), fourth (52 Å), and sixth (26 Å) InGaAs marker layers using 1 keV ion energy for different incident angles. (b) Exponential decay lengths derived from the slope at the trailing edge for the individual InGaAs marker layers as a function of depth.
(a) Normalized -profiles (Atomika 4500) around the position of the second, fourth, and sixth InGaAs marker layers using 500 eV ion energy for different incident angles. (b) Exponential decay lengths as a function of depth.
(a) Angular dependence of SIMS ion intensity ratios as a function of depth for 1 keV ion beam sputtering. (b) Angular dependence for 500 eV .
Relative sputter yield derived from measured erosion rate for different impact conditions. Sputter yield data have been fitted by a equation (dashed lines) at higher oblique angles .
(a) SIMS (Cameca Wf) In-concentration profiles (left axis) and characteristic GaAs matrix intensity profiles (right axis) for 1 keV impact energy and detection of cluster ions. (b) Linear correlation between aerial In-doses (SIMS) and/or thicknesses (TEM) for the individual InGaAs marker layers and MBE shutter opening time for InGaAs growth.
(a) In-concentration profiles and GaAs matrix reference ion intensity profiles at 1 keV and 650 eV ion impact energy. Depth scale reconstruction has been established assuming a constant erosion rate while matching the spacing between the second and fourth InGaAs markers to the TEM spacing. (b) Close-up of In-profile around the first InGaAs marker layer, showing substantial depth resolution improvement at 650 eV impact energy. Note that 650 eV profile has been shifted in depth by 30 Å to align the leading edges.
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