Abstract
As excitation laser intensity increases, due to the change of Coulomb interaction energy between the recombined donors and acceptors, the donor-acceptor pair (DAP) transition energy shifts to high energy (i.e., blueshift).1 Usually this blueshift is very small (<3 meV) in bulk semiconductor materials with low impurity density.1–2 Previously, we reported a large blueshift of 11 meV in GaAs/AlGaAs compensation-doped quantum wells (QWs) with the doping density of 3 × 1017 cm−3.3 However, at the relatively high laser intensities, the free-excitonic emission dominates the photoluminescence (PL) spectrum with the DAP transition as a shoulder. The peak energy of the DAP transition was obtained only after the PL profile was decomposed into two peaks. As a results, we did not directly observe the large amount of the blueshift. Here, we report our results on direct observation of an anomalously large blueshift as large as 12 meV in GaAs/AlGaAs QWs with low residual (undoped) impurity densities. Each PL spectrum consists of only the DAP transition peak within the entire range of pump intensities. Therefore, the amounts of blueshift determined here are much more accurate than those in Ref. 3.
© 1999 Optical Society of America
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