Near-infrared electroluminescence of furnace or CO2 laser annealed si-rich SiO2 with structural defects and Si nanocrystals - art. no. 619515

Abstract

Electroluminescence of the CO2 laser annealed PECVD-grown silicon-rich silicon oxide (SRSO) based metal-oxide-semiconductor diode with embedded Si nanocrystals is demonstrated. The structural and optical properties of a CO2 laser rapid thermal annealed Si-rich SiO1.25 film are investigated. The color of SiO1.25 film changes from light yellow to dark-yellow as the CO2 laser annealing intensity enlarges from 1.5 to 13.5 kW/cm(2). Such a color change is mainly attributed to both the increasing absorption coefficient and refractive index of the SiO1.25 film under the precipitation of Si nanocrystals. The thickness of the SiO1.25 film was thinned during the dehydrogenated process at a slightly lower laser intensity of 4 kW/cm(2), while the complete dehydrogenation is observed after annealing for 1.4 ms associated with a thickness shrinking from 280 mn to 240 nm. TEM analysis and pbotoluminescence spectroscopy at 806 nm reveal that the Si nanocrystals with maximum diameter and density of 5.3 nm and 10(18) cm(-3), respectively, can be precipitated as the CO2 laser intensity increase to an ablation threshold intensity of 5.8 kW/cm(2). The laser ablation introduces numerous structural defects and causes the anomalous absorption as well as photoluminescence at blue-green wavelengths in the SiO1.25 film. From the reflection spectra with enlarged interfering fringe amplitude, the increasing refractive index (from 1.57 to 1.88) of the SiO1.25 with increasing laser intensity can be concluded. In comparison with that of the quartz or as-grown sample, the red-shifted optical bandgap energy of the CO2 laser-annealed SiO1.25 film from 5.4 eV to 4 eV has evidenced the effect of the strong blue-green absorption on the oxygen vacancy defect. The forward turn-on voltage and current density of the ITO/CO2 laser annealed SRSO/p-Si/Al MOS diode are 79 V and 33 mu A/cm(2), respectively. The maximum output power of 29 nW associated with a P-I slope of 4.4 mW/A is determined.