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Schematic representation of the spatial control of intermixing degree: (a) the surface defects modulation during plasma exposure using a thick mask layer and (b) the annealing step to induce different degree of intermixing. The high mobility of mobile point defects on the near sample surface leads to the uniform distribution at the QW active region for modulated area of smaller than the lateral diffusion length.
Normalized PL spectra at of (a) QWs, (b) QWs, and QWs material for (i) as-grown, (ii) annealed only, and (iii) intermixed samples. The annealing was done at the thermal stability threshold, at which the as-grown sample only experiences a minor band gap shift due to thermal process.
The PL spectra obtained from a multiple width QWs probe structure (a) as grown, (b) after plasma exposure for , and (c) subsequent annealing on the exposed sample at for .
(a) The optical microscope picture of the eight different exposed area coverage (dark area) using stripe layer (bright area) as a defects modulation mask, varying from 0 (top left), 30, 40, 45, 50, 75, 90, and 100% (bottom right). (b) The correlation between band gap shift and linewidth of QWs laser structure from PL measurements at with the percentage of plasma exposure window area.
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