Interface states and deep-level centers in silicon-on-insulator structures

Deep-level centers in a split-off silicon layer and trap levels were studied by deep-level transient spectroscopy both at the Si/SiO₂ interface obtained by direct bonding and also at the Si(substrate)/〈thermal SiO₂〉 interface in the silicon-on-insulator structures formed by bonding the silicon wafers and delaminating one of the wafers using hydrogen implantation. It is shown that the Si/〈thermal SiO₂〉 interface in a silicon-on-insulator structure has a continuous spectrum of trap states, which is close to that for classical metal-insulator-semiconductor structures. The distribution of states in the upper half of the band gap for the bonded Si/SiO₂ interface is characterized by a relatively narrow band of states within the range from E _c ?0.17 eV to E _c ?0.36 eV. Furthermore, two centers with levels at E _c ?0.39 eV and E _c ?0.58 eV are observed in the split-off silicon layer; these centers are concentrated in a surface layer with the thickness of up to 0.21 µm and are supposedly related to residual postimplantation defects.