Oxygen-deficient centers and excess Si in buried oxide using photoluminescence spectroscopy

Defects in buried oxide (BOX) in Si prepared from the separation by implantation of oxygen (SIMOX) technique under various preparation conditions such as doses of oxygen $\left[\right(0.39\mathrm{}–1.9)\times {10}^{18}{\mathrm{cm}}^{\mathrm{-}2}]$ and anneal temperatures (1310–1350 °C) were investigated by a photoluminescence technique using synchrotron radiation as a light source. Under excitation at 5.0 eV at room temperature, all the SIMOX BOX samples typically exhibit a broad photoluminescence (PL) band in the range of 2–3 eV, which can be deconvoluted into three Gaussian components at 3.1, 2.6–2.8, and 2.4 eV. The 3.1- and 2.6–2.8-eV bands have lifetimes of about 2–45 ns, while the 2.4-eV band has a much longer lifetime. In addition, some high-dose SIMOX BOX’s prepared with multiple oxygen implant steps show a 4.4-eV PL band with a lifetime of about 4 ns associated with a form of oxygen-deficient centers (ODC’s) called ODC(II) in $a-{\mathrm{SiO}}_2,$ which were suppressed by a supplemental oxygen implantation. The behavior of the short-lived 2–3-eV PL components was sensitive to the oxygen doses and anneal temperatures, and conditions that tended to increase the 2–3-eV PL tended to decrease the 4.4-eV band. Etchback experiments of the BOX layer show that the defects responsible for the 2–3-eV band were located at the BOX close to the superficial Si/BOX interface, while those for the 4.4-eV band exist throughout the whole BOX layer. Comparison with high-temperature oxide grown on Si at 1350 °C suggests that the postimplantation, high-temperature anneal results in the generation of defects responsible for the short-lived 2–3-eV bands. Based on the similarities with the PL bands in Si clusters in ${\mathrm{SiO}}_2,$ we conclude that the 2–3-eV bands in the BOX’s are associated with Si clusters in ${\mathrm{SiO}}_2.$