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.

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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.

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We have studied the role of boron ion energy in the engineering of dislocation loops for silicon light-emitting diodes ͑LEDs͒. Boron ions from 10 to 80 keV were implanted in ͑100͒ Si at ambient temperature, to a constant fluence of 1 ϫ 10 15 ions/ cm 2 . After irradiation the samples were annealed for 20 min at 950°C by rapid thermal annealing. The samples were analyzed by transmission electron microscopy and Rutherford backscattering spectroscopy. It was found that the applied ion implantation/thermal processing induces interstitial perfect and faulted dislocation loops in ͕111͖ habit planes, with Burgers vectors a /2͗110͘ and a /3͗111͘, respectively. The loops are located around the projected ion range, but stretch in depth approximately to the end of range. Their size and distribution depend strongly on the applied ion energy. In the 10 keV boron-implanted samples the loops are shallow, with a mean size of ϳ30 nm for faulted loops and ϳ75 nm for perfect loops. Higher energies yield buried, large, and irregularly shaped perfect loops, up to ϳ500 nm, coexisting with much smaller faulted loops. In the latter case much more Si interstitials are bounded by the loops, which are assigned to a higher supersaturation of interstitials in as-implanted samples, due to separated Frenkel pairs. An interesting phenomenon was found: the perfect loops achieved a steady-state maximum size when the ion energy reached 40 keV. Further increase of the ion energy only increased the number of these large loops and made them bury deeper in the substrate. The results of this work contribute to laying a solid ground in controlling the size and distribution of dislocation loops in the fabrication of silicon LEDs.

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The relaxation of compositionally graded InGaAs buffers, with and without uniform cap layers, has been studied. Simple InGaAs linear-graded layers on GaAs substrates never reach complete relaxation. The residual strain in these structures produces a dislocation-free strained top region while the rest of the buffer is nearly completely relaxed through misfit dislocations, as observed by transmission electron microscopy (TEM). This strained top region is analyzed and its thickness compared with theoretical calculations. The effects of different cap layers on the relaxation behavior of the graded buffer has been studied by double crystal x-ray diffraction, TEM, and low temperature photoluminescence, and results compared with predictions of the models. The optical quality of the cap layer improves when its composition is close to the value that matches the lattice parameter of the strained surface of the grade. The design of linear graded buffers having a strain-free cap layer with high crystalline quality is discussed.