There is an urgent requirement for an optical emitter that is compatible with standard, silicon-based ultra-large-scale integration (ULSI) technology. Bulk silicon has an indirect energy bandgap and is therefore highly inefficient as a light source, necessitating the use of other materials for the optical emitters. However, the introduction of these materials is usually incompatible with the strict processing requirements of existing ULSI technologies. Moreover, as the length scale of the devices decreases, electrons will spend increasingly more of their time in the connections between components; this interconnectivity problem could restrict further increases in computer chip processing power and speed in as little as five years. Many efforts have therefore been directed, with varying degrees of success, to engineering silicon-based materials that are efficient light emitters. Here, we describe the fabrication, using standard silicon processing techniques, of a silicon light-emitting diode (LED) that operates efficiently at room temperature. Boron is implanted into silicon both as a dopant to form a p-n junction, as well as a means of introducing dislocation loops. The dislocation loops introduce a local strain field, which modifies the band structure and provides spatial confinement of the charge carriers. It is this spatial confinement which allows room-temperature electroluminescence at the band-edge. This device strategy is highly compatible with ULSI technology, as boron ion implantation is already used as a standard method for the fabrication of silicon devices.

No abstract

The relationship between the CHE2 locus of serum cholinesterase (BChE) and adult human weight was studied in a sample of 225 CHE2 C5+ individuals and 225 CHE2 C5- controls matched for sex, height, age and race. With respect to the intensity of the C₅ band staining (scored 1–6), 113 individuals had faint C₅ bands (scores 1–3) and 112 intense C₅ bands (scores 4–6). The individuals with intense CHE2 C5+ phenotype showed a significantly lower mean adult weight (64.66 ± 0.73 kg) when compared to their controls (70.59 ± 0.97 kg) and a significant reduction in weight variance (59.81 and 105.18, respectively). Individuals with faint C₅ bands, although showing a negative correlation between weight and C₅ band intensity, did not differ from their controls in mean weight.

The optically active carbon related G‐center is attracting great interest because of evidence that it can provide lasing in silicon. Here a technique to form the G‐center in silicon is reported. The carbon G‐center is generated by implantation of carbon followed by proton irradiation. Photoluminescence measurements confirm the controlled formation of high levels of the G‐center that, importantly, completely dominates the emission spectrum. Unlike previous methods of introducing the G‐center the current approach significantly is truly fully compatible with standard silicon ULSI (ultralarge scale integration) technology.

No abstract