EXCITONS IN A DENSE 2-DIMENSIONAL ELECTRON-GAS AT A SEMICONDUCTOR SURFACE

The Fermi-edge singularity, increasing with increasing 2D electron den sity, is observed in the recombination radiation line of 2D electrons and nonequilibrium holes in luminescence spectra of [100] silicon meta l-oxide-semiconductor structures. A new effect of anisotropic paramagn etic reduction of the Fermi-edge singularity proves that this singular ity transforms itself into emission line of real excitons in a dense 2 D electron gas before the second electron subband occupation.