Correlation of charge trapping and electroluminescence in highly efficient Si-based light emitters

Silicon based light emitters are of great interest for future integrated optical systems. One possible approach for the formation of such devices is ion beam synthesis. Thermally grown SiO2 layers (80 nm) were implanted with germanium ions at energies of 30…50 keV to peak concentrations of 1…6 at%. Rapid thermal annealing was performed at 1000°C for 1…150 s under a nitrogen atmosphere in order to form luminescence centers. In previous investigations we observed strong photo- and electro-luminescence (EL) in the blue/violet wavelength range from such layers. In this paper we correlate these optical properties to effects of charge trapping which were observed by using a combination of capacitance-voltage (CV) and current-voltage (IV) methods. Electron trapping occurs at low electric fields. However, at high electric fields (>8MV/cm), which are typically required for the excitation of the defect related EL, positive charge trapping occurs. This might be attributed to hole trapping at oxygen deficiency centers - probably the same defects which cause the EL.