Polaritons composed of 2DEG Fermi‐edge transitions in a GaAs/AlGaAs modulation doped quantum well embedded in a microcavity

The reflection and photoluminescence spectra of a GaAs/Al0.1Ga0.9As structure consisting of a modulation doped quantum well embedded in a microcavity (MC) were studied under a perpendicularly applied magnetic field (B < 7T) and at T = 2K. The two dimensional electron gas (2DEG) density in the quantum well was 1.8 × 1011 cm−2. Sharp lines are observed, whose energy dependence on the energy of the MC‐confined photon identifies them as cavity polaritons, similar to those observed in structures of an undoped quantum well embedded in a MC. We show that they arise from the strong coupling between the MC‐confined photons and interband transitions above the Fermi edge or inter‐Landau level transitions of the 2DEG.