AFM images and linescans of GaAs surfaces after LDE with [(a) and (b)] Ga, [(c) and (d)] , and [(e) and (f)] In. Note the different scales in (b), (d), and (f). As indicated, dashed and full lines are recorded in  and crystal direction, respectively.
Hole and hill densities as function of the In content in the etchant. The insert shows the sum of the hill and hole densities (symbols) together with an exponential fit (line). A characteristic energy is determined from the fit.
(a) 3D AFM image of a typical nanohole with wall fabricated using LDE with . (b) Schematic profile of a LDE nanohole with wall: is outer radius; : inner radius; is depth; and is angle between the substrate surface and the sidewall of the holes.
Symbols: measured outer radius of quantum rings fabricated with LDE as function of the In content . A characteristic energy is determined from a logarithmic plot shown in the inset. Lines: exponential fit with indicated .
Depth of the nanoholes in dependence on the In content of the etchant. The inset shows the calculated angle between the substrate surface and the inner sidewall of the holes which is approximately constant with .
3D AFM image of an hole. Along direction we find a wall height of 13 nm, which is about twice as high as the 7 nm in  direction.
(a) Low temperature PL measurements of a single GaAs quantum ring in AlGaAs . The excitation power was varied from 0.7 up to 210 nW. The inset shows a magnification of the peaks at 1.625 eV at an excitation power varied from 0.7 up to 22 nW. (b) Low temperature PL of an ensemble of quantum rings fabricated with InGa LDE in an AlGaAs matrix. The In content in the etchant is . The labeled peaks are attributed to the GaAs substrate, the AlGaAs layers, and the quantum rings. The insert shows PL spectra from a single quantum ring at excitation power varied from 0.7 up to 22 nW. The spectra in (a) and (b) are vertically shifted for clarity.
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