Condensates of exciton-polaritons, quasiparticles created from coherent strong coupling between photons and excitons, have opened the way for studies of novel out of equilibrium physics, where competition between gain and loss drives the rich dynamics of the system, although keeping many similarities to photon lasers or Bose-Einstein condensates. Disorder, which is inevitably present in semiconductor microcavities, plays often a crucial role in the formation and dynamics of a polariton condensate in moderate quality structures. In my talk, I will present investigations of dynamical polariton condensation in a disordered GaAs-based microcavity containing high In-content quantum wells. Scattering of polariton waves on strong sample disorder resulted in the occupation of ghost branch states, which have negative energy with respect to the initial energy . Moreover, I will present complex oscillatory dynamics of the condensate formation in the time domain, which is a result of disorder combined with the long-living excitonic reservoir, which is the gain source for the condensate .
 M. Pieczarka et al., Phys. Rev. Lett. 115, 186401 (2015)  M. Pieczarka et al., Sci. Rep. 7, 7094 (2017)