Photoluminescence spectral evolution from 2DEG-free hole to charged excitons in modulation-doped GaAs/AlGaAs quantum wells

We report on a detailed study of the photoluminescence (PL) in high quality GaAs/AlGaAs quantum wells containing a two‐dimensional electron gas. The 2DEG density was varied by optical depletion (with He–Ne laser illumination) in the range of n2D = (7–3) × 1010 cm−2. The n2D‐dependent PL spectra were studied under a perpendicularly applied magnetic field B < 12 T at TL = 0.3 and 1.5 K. The evolution from free hole‐2DEG to charged exciton PL with decreasing n2D or with increasing magnetic field is attributed to the appearance of regions containing localized electrons as the filling factor decreases below ν = 0.4–0.3. This results in simultaneous PL of the free hole‐2DEG originating from electron puddles and of charged exciton from regions with localized electrons. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)