Energy Transfer from Silicon Nanocrystals to Er Ions Embedded in Silicon Oxide Matrix

Silicon (Si) based light emitting devices have drawn much attention for the integration of electronic and photonics. Si nanostructures (amorphous clusters or crystals) have been recognized as good candidates for effective light emitting devices (Bulutay, 2007; Seino et al., 2009; Takagahara & Takeda, 2007; Wolkin et al., 1999). However, photons emitted by Si nanostructures can be reabsorbed by Si waveguides due to the higher photon energy compared to bulk Si bandgap. To overcome this problem, Erbium (Er) doped Si nanostructures embedded in SiO2 matrix has been extensively studied (Fujii et al., 2004; Heitmann et al., 2003; Kik & Polman, 2001; Polman & Veggel, 2004; Savchyn et al., 2007, 2008). Si nanostructures can be excited optically or electrically, then transfer the energy to Er3+ ions which then decay radiatively giving emission peaked at 1.53μm, which coincides with the telecommunication wavelength. Hence, light sources made by this material system (Er3+ ions doped Si nanostructures embedded in SiO2 matrix) in the integrated Si platforms can be used directly with telecommunication devices. To date, however, one of the main challenges of this material system is the low energy transfer efficiency from Si nanostructures to Er3+ ions, which we are going to address in this chapter. To increase the energy transfer efficiency, the mechanism of the energy transfer must be well understood. Prior to 2007, many research works reported that the main energy transfer mechanism is from Si nanocrystals to Er3+ ions (Fujii et al., 2004; Heitmann et al., 2003; Kik & Polman, 2001; Polman & Veggel, 2004). However, recently, in 2007 and 2008, one leading group in the field suggested that defect mediated energy transfer was the dominant mechanism (Savchyn et al., 2007, 2008). In their work (Savchyn et al., 2007, 2008), the origin of defects that transfer energy to Er3+ ions was not discussed. The controversial in the energy transfer mechanism has created much difficulty in improving Er3+ emission efficiency. The approach to improve Er3+ emission efficiency will clearly very much depend on the dominant mechanism of the energy transfer to Er3+ ions, whether the defects or the Si nanocrystals are the dominant factor for the energy transfer. In this chapter, we present our work on different energy transitions from defects and from Si nanocrystals and their energy transfer efficiency to Er3+ ions. Bulk Silicon Rich Oxide