The self-consistently calculated electronic structure of -doped GaAs/AlGaAs superlattice-barrier QW structure with (a) 2.5, (b) 3.1, (c) 3.7, and (d) 4.5 nm wide wells. Solid (dashed) lines show the wave function moduli squared of the heavy-hole (light-hole) states, with the baseline offset according to their energy, and the heavy solid line is the potential (v.b. top) in the actual structure, with interdiffusion accounted for ( is used in these figures). The “inverted energy scale” picture is used, i.e., the ground hole state is the lowest.
The dependence of (a) HH1-HH2 and (b) HH1-LH2 absorption peak energies on the interdiffusion length in the four structures. The horizontal lines show the experimental values.
The calculated absorption profiles for -polarization (thin solid lines) and -polarization (thin dashed lines), and measured profiles (thick solid and dashed lines, respectively), for (a) 2.5, (b) 3.1, and (c) 3.7 and 4.5 nm wide QWs (the last two were grown on the same sample). All data are at 17 K, and in case of the 3.1 nm QW the -polarized absorption at 300 K is also shown. The dash-dotted line for the 2.5 nm QW is the absorption profile in the modified structure, with 0.75 (1.23) nm wide GaAs (AlAs) superlattice layers. The homogeneous linewidths (FWHM) used to reproduce the measured spectra at 17 K are: 12 meV (40 meV), 19 meV (46 meV), and 16 meV (40 meV) for the HH1-HH2 (HH1-LH2) transitions in 3.1 nm, 3.7 nm, and 4.5 nm QW, respectively. The HH1-HH2 absorption in the 2.5 nm QW is plotted with a 16 meV homogeneous width (or 18 meV in the modified structure, dash-dotted line), while the measured HH1-LH2 absorption profile was difficult to resolve for fitting purposes and is not shown. At 300 K the homogeneous linewidth of 20 meV was used for the 3.1 nm QW.
The widths of resonances (FWHM, in meV units) in the four structures with different central QW widths, for the interdiffusion length . A zero value for the width means that the state is strictly discrete.
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