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We have observed an anomalous photovoltaic effect in films of Si nanocrystals embedded in SiO2. Using conductive-probe atomic force microscopy and global transport measurements, we found, close to the percolation threshold of the Si crystallite phase, a large photovoltaic effect of up to about 7V. Following the dependence of this effect on the size of the Si nanocrystals and on the relative tip position with respect to the counterelectrode, we suggest a model based on charge separation of excited electron-hole pairs governed by the size-dependent quantum confinement and charging energies.

In this paper, we report on an increase in emission intensity of up to 10 nW/µm2 that has been realized with a new novel two junction, diagonal avalanche control, and minority carrier injection silicon complementary metal–oxide–semiconductor (CMOS) light emitting device (LED). The device utilizes a four-terminal configuration with two embedded shallow n+p junctions in a p substrate. One junction is kept in deep-avalanche and light-emitting mode, while the other junction is forward biased and minority carrier electrons are injected into the avalanching junction. The device has been realized using standard 0.35 µm CMOS design rules and fabrication technology and operates at 9 V in the current range 0.1–3 mA. The optical output power is about one order of magnitude higher for previous single-junction n+p light-emitting devices while the emission intensity is about two orders of magnitude higher than for single-junction devices. The optical output is about three orders of magnitude higher than the low-frequency detectivity limit of silicon p–i–n detectors of comparable dimensions. The realized characteristics may enable diverse optoelectronic applications in standard-CMOS-silicon-technology-based integrated circuitry.

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