VISIBLE-LIGHT EMISSION FROM SI MATERIALS

The photoluminescence of electrochemically etched silicon under excitation in the wavelength range from 325 to 514 nm is described by a single energy gap (of order of 1.9 eV). The Raman spectra can be explained by a Gaussian phonon confinement to a geometrical structure size of about 3 nm. In addition, the novel method of spark erosion for a non-liquid preparation of light-emitting silicon has been used, and it is shown that the light emission spectrum, apart from its overall intensity, is independent of environment gas species (N-2, O-2 or H-2). In areas of higher electric field strength, presumably leading to a smaller effective size, a blue shift is observed in all these cases. This appears to rule out any siloxene-derivate models and suggests a quantum confinement as the basic phenomenon.