Oscillator Strengths for Neutral, Charged, and Scattered Excitons in CdTe Quantum Wells Containing a 2D Electron Gas

Abstract

Absorption spectra have been measured for a 10 nm CdTe(0.3%Mn) quantum well with electron concentration ne variable up to 1.5×10 cm−2. Following recent theory appropriate to low ne, here ≈ 0.1/πaB, the spectra are interpreted in a “strong exciton” model, where the initial oscillator strength of the excitonic resonance (X) is conserved, with screening and phase-space filling effects negligible. As ne increases in zero-field and as the filling factor ν increases in magnetic field, the intensity of X is transferred to: (i) trion processes, namely exciton-one electron scattering and the trion resonance (T ), and (ii) quatron processes, namely exciton-two electron scattering and trion-one electron scattering. In magnetic field, the threeand four-body scattering processes become discrete, combined “exciton and cyclotron” and combined “trion and cyclotron” excitations that take all the intensity of X and T for ν >∼ 1 and ν > 2, respectively.