Investigation of emitting centers in SiO2 codoped with silicon nanoclusters and Er3+ ions by cathodoluminescence technique

Abstract

Electroluminescence from Er-doped Si-rich silicon nitride light emitting diodes Appl. Phys. Lett. 97, 081109 (2010); 10.1063/1.3483771Resonant structures based on amorphous silicon suboxide doped with Er 3 + with silicon nanoclusters for an efficient emission at 1550 nm Current transport and electroluminescence mechanisms in thin SiO 2 films containing Si nanocluster-sensitized erbium ionsThis study reports on the investigation and characterization of the different emitting centers within SiO 2 codoped by Er 3+ ions and silicon-excess. Erbium doped silicon-rich silicon oxide ͑SRSO:Er͒ thin films, fabricated by magnetron cosputtering at 500°C, were analyzed by means of cathodoluminescence. The CL spectra of SRSO, Er-doped SiO 2 and SRSO:Er were recorded and compared for various annealing temperatures. It was found that some specific optically-active point-defects called silicon-oxygen-deficient centers ͑SiODCs͒ are present in all kinds of samples. In the layers containing some excess Si, the phase separation between Si nanoclusters ͑Si-ncs͒ and SiO 2 is observed when the annealing temperature reaches and exceeds 900°C. The formation of Si-nc increases with annealing at the expense of SiODCs that was assumed to act as seeds for the growth of Si-nc. For SRSO:Er samples, the contribution of SiODCs overlaps that due to Er 3+ transitions in the visible range. The emissions from SiODCs are drastically reduced when an SRSO sample is doped with Er ions, whereas the Er emissions in the visible range start to be distinctly observed. We propose a scenario of energy transfer from SiODCs toward the Er ions, especially as the emissions from the Si-based entities ͑SiODCs, Si-nc͒ and from some transitions of Er ions are located in a same visible broad range.

Bipolar pulsed excitation of erbium-doped nanosilicon light emitting diodes

“…Electrical charge transport in our Si-NC LEDs is due to electric field-enhanced tunneling of electrons with the involvement of either defects [14][15][16] or confined energy states of Si-NCs. 17,18 Erbium implantation produces deep energy trapping levels which change the transport properties of the Si-NC LED.…”

Silicon nanocluster sensitization of erbium ions under low-energy optical excitation

“…23 On the other hand, the silicon excess related "luminescence center" erbium sensitization has been well established in a wide range of excitation energies. 15,29 However, an even distribution in the energy of these defect states is expected, 15,28,29 with wavelength dependence of effective cross-section for erbium sensitization mirroring one of the silicon nanoclusters. 15 Moreover, the energy transfer to higher energy states of Er 3þ ions would be still possible for this sensitizing mechanism at the excitation energies we use, 12,[28][29][30] in contrast to what we observe.…”

“…7,11,28 The very fast PL decay contribution (Fig. 3, inset), in our samples, has been experimentally related to the presence of the silicon nanoclusters (silicon excess) in the silicon dioxide matrix 7,10,29 6,23 Considering that the contribution of this component to the total PL is practically negligible and that the elucidation of its exact origin falls out of the scope of this work, it will not be investigated further.…”

Origin of the visible emission of black silicon microstructures

“…Recent reports demonstrate room-temperature visible light emission in silicon in low-dimensional system, such as wurtzite silicon nanowires, 1,2 nanocrystals, 3,4 nano-pillars, 5 porous silicon, [6][7][8] and silicon/insulator superlattices. 9,10 In addition, a simple femtosecond-laser (fs-laser) processing technique can drastically change the optical properties of silicon. In particular, the fs-laser processed silicon (black silicon) has gained increased interest due to the peculiar optical properties, including the enhanced sub-bandgap absorption [11][12][13] and visible light emission.…”