Silicon based IR light emitters

Abstract

A new concept for Si‐based light emitting diodes (LED) capable of emitting at 1.5 μm is proposed. It utilizes D‐band radiation from dislocations in Si. Whether a dislocation network created in a reproducible manner by Si wafer direct bonding or dislocation loops produced by Si ion implantation are employed. It is also stated that dislocation loops do not lead to the strong band‐to‐band electroluminescence at 1.1 μm of p‐n diodes, as it was predicted in the literature. A MOS‐LED (Fig. A) and p‐n LEDs emitting at 1.5 μm are demonstrated by the authors. The maximum efficiency that could be achieved at room temperature is close to 1%. Levels in the bandgap which are probably involved in the formation of the D1‐line at 1.5 μm are revealed. Moreover, the observation of the Stark effect for the D1‐line is reported. Namely, a red/blue‐shift of peak position was observed in electro‐ and photo‐luminescence when the electric field in the p‐n LED was increased/lowered. This effect may allow realization of a novel Si‐based light emitter with electric field modulated emission wavelength. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electronic and Optical Properties of Dislocations in Silicon

“…When the network is positioned near the Si/oxide interface, the radiative recombination is dominated by the D1-line at about 1.5 μm. This is clearly seen from the EL spectra shown in Figure 24b (note that band-band-luminescence around 1.1 μm appears without the dislocation network [108]). The MOS-LED on p-type Si, with a dislocation network at a depth of about 45 nm, consisted of a 134 nm thick Ti gate deposited on 1.8 nm thick tunnel silicon oxide, see TEM micrographs shown in Figure 24c.…”

“…Impact of misorientation/structure on the luminescence spectra of dislocation networks: (A) twist angle of ϑ twist = 3˝, dominating D1 peak; and (B) twist angle of ϑ twist = 8.2˝, dominating D3 peak. The same tilt angle of ϑ twist = 0.2˝exists in both cases [108].…”

“…The D1-line is probably formed by the transition between one of the shallow 1D-bands (EDe, EDh) and a deeper state, compare e.g. [108,109]. The origin of the D2-line is still under discussion.…”

“…The band diagram of a tunnel MOS-LED with a dialocation network on p-type Si is schematically represented in Figure 24a, see also [108,117]. When the network is positioned near the Si/oxide interface, the radiative recombination is dominated by the D1-line at about 1.5 µm.…”

Defect luminescence at grain boundaries in multicrystalline silicon

“…A similar defect scheme to the here described "sandwich" model has already been developed for the D1 luminescence in dislocated silicon [7]. In that case a shallower level is placed below the conduction band and a deeper level is placed above the valence band.…”