Spectroscopy of electroreflection, the electron band structure, and the mechanism of visible photoluminescence of anisotropically etched silicon

We present the results of studies of electroreflection in the 1.1-4.4 eV sp ectral range, of electron Auger spectroscopy, and of electron diffraction i nvolving the photoluminescent Si-SiO2 system prepared via anisotropic chemi cal etching of the Si(100) surface. These results are explained on the basi s of a four-layer model of the band structure and energy transition diagram for a system with a quantum well at the silicon surface, surface electron states at the boundary, and a gradient of the band potential in the transit ion layer. We find that light-emitting silicon remains an indirect-gap semi conductor and that the visible photoluminescence is due to direct recombina tions of the light-excited electrons and holes in the quantum well at the c enter of the Brillouin zone with the participation of the band of deep loca lized states, which is due to the presence of oxygen at the silicon surface . (C) 1999 American Institute of Physics. [S1063-7761(99)01811-9].