Polaritons in microcavities containing a two-dimensional electron gas

We review the spectroscopic and dynamic properties of cavity polaritons in a X-wide GaAs/GaAlAs microcavity (MC) structure having a single GaAs/AlAs quantum well in which a variable density two-dimensional electron gas (2DEG) is photoexcited, with a density in the range 0 n(e) 5 x 10(11) cm(-2). The main observed effects that will be discussed here are: (a) photoexcitation of negatively charged polaritons. These polaritons result of the coupling of the MC photon and the negatively charged excitons. They appear at low temperatures (T 25 K), in the range of low 2DEG densities (n(e) 5 x 10(10) cm(-2)), and their coupling strength increases as rootn(e). (b) The effect of electron-polariton scattering on the polariton spectral linewidth, its complex dependence on the detuning energy, and the electron-induced transition from strong to weak coupling regimes, as n(e) increases. (c) The efficient polariton transfer across the relaxation bottleneck in the lower branch induced by electron-polariton scattering, and the resulting non-linear dependence of the polariton photoluminescence intensity on n(e).