Regular Dislocation Networks in Si. Part II: Luminescence

Abstract

Regular dislocation networks formed as a result of the direct bonding of Cz-Si wafers with oxide remnants on the pre-bonding surfaces were investigated. Besides the dislocation network, oxide precipitates were detected at the bonding interface. The precipitate density across the network was ~5×1010 cm-2, except small irregularly distributed circular areas, several mm in diameter, where the density was remarkably lower (<5×108 cm-2). The dislocation network structure was not affected by the change in the precipitate density. Photoluminescence spectroscopy (PL) and light beam induced current (LBIC) mapping were applied for characterization of such dislocation networks. For the locations with high precipitate density, PL signal from dislocations and that from the band-to-band transitions were enhanced. On the other hand, the LBIC results indicated that oxide precipitates are active recombination centers and thus should suppress the observed radiative transitions. The controversy can be explained in the assumption that the D-band PL signal increases due to scattering of excitation light by the precipitates and due to related expansion of the excitation area of the dislocation network. The light reflection from the precipitate layer also enhances the detected band-to-band PL signal. The shape of PL spectra from the samples in the range of photon energies 0.75 – 1.15 eV was not influenced by the oxide precipitates.