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 x 10(11) 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.