Germanium negative-ion implantation into SiO2 layer on Si: Photoluminescence properties and oxidation state of Ge atoms in subsequent heat treatment

Abstract Photoluminescence properties (PL) and oxidation state of Ge atoms implanted into a thermally grown SiO 2 layers have been investigated. The samples were prepared by Ge negative-ion implantation at multi-energies of 10–50 keV with various Ge concentrations of 0.5–6 at.% and subsequent two-stage annealing in N 2 at a flow rate of 50 ml/min and in decompressed air at flow rate of 10 ml/min at temperatures of 600 °C–900 °C for 1–3 h. Results showed that the PL emission with a peak at 390 nm depended on both Ge concentration and subsequent annealing temperature. For the low Ge concentrations of 1–1.4 at.%, the strong PL emission could be obtained just after 1 h annealing in N 2 at 700–800 °C. For the high Ge concentration of 3 at.%, the PL emission was improved and increased after annealing in decompressed air, but it still was weaker than that of the Ge sample at 1.4 at.%. XPS analysis showed that almost 60% of Ge atoms were oxidized to form GeO and GeO 2 , even as implanted sample and this oxidation decreased to 35% after N 2 annealing. The induced defects of SiO 2 as absorption center recovered while the oxygen defects (ODC) of GeO 2 were reduced during annealing in N 2 . The deoxidation of GeO 2 is suppressed by annealing in decompressed air flow. Based on the obtained results, we have discussed the best way of heat treatment to increase ODC by two-stage annealing in N 2 and in decompressed air.