Soft x-ray emission spectroscopy studies of the electronic structure of silicon supersaturated with sulfur

We apply soft x-ray emission spectroscopy (XES) to measure the electronic structure of crystalline silicon supersaturated with sulfur (up to 0.7 at. %), a candidate intermediate-band solar cell material. Si L-2,L-3 emission features are observed above the conventional Si valence band maximum, with intensity scaling linearly with S concentration. The lineshape of the S-induced features change across the insulator-to-metal transition, indicating a significant modification of the local electronic structure concurrent with the change in macroscopic electronic behavior. The relationship between the Si L-2,L-3 XES spectral features and the anomalously high sub-band gap infrared absorption is discussed. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3643050]