Currently, electrical interconnections based on metal lines represent the most important limitation on the performances of silicon-based microelectronic devices. The parasitic capacities generated at the metal/insulator/metal capacitors present in the complex multilevel metallization schemes actually used, the intrinsic resistivity of the metal lines, and the contact resistance at the metal/metal interfaces constitute the main contributions to the delay in the signal propagation. Recently, a reduction of the delay times was achieved by replacing the traditional metallization schemes based on Al and SiO 2 with new materials, such as copper-based alloys and low-dielectricconstant insulating layers, but as soon as the minimum feature size of the devices will be further reduced, the delay resulting from metal interconnections will again represent an unacceptable bottleneck for device performances.[1] A definitive solution to this problem could be the use of optical interconnections for the transfer of information inside a chip or for chip-to-chip communications. To develop this strategy, siliconcompatible materials and devices able to generate, guide, amplify, switch, modulate, and detect light are needed. Recent major breakthroughs in this field have been the observation of optical gain in Si nanocrystals, [2] the development of a Si Raman laser, [3] the realization of a high-speed Si electro-optic modulator, [4] and the observation of electroluminescence from ultrapure Si diodes [5] and Si nanocrystal field-effect transistors. [6] A primary requirement for the materials proposed for the above applications is compatibility with current Si technology. However, because Si is intrinsically unable to efficiently emit light, owing to its indirect bandgap, it is evident that the main limitation to the approach described above is the lack of an efficient silicon-based light source. Among the efforts of the scientific community to efficiently produce photons from silicon, the introduction of light-emitting impurities, such as erbium ions, has a leading role. A relevant advantage of this approach is that standard silicon technology can be used to introduce erbium as a dopant and to process the material. Furthermore, Er ions emit at 1.54 lm, which is a strategic wavelength for telecommunication because it corresponds to a minimum in the loss spectrum of the silica optical fibers. Incorporation of Er in crystalline silicon (c-Si) emerged as the first promising method to turn silicon into a luminescent material, [7] but doping concentration was limited (ca. 1 × 10 18 cm -3) by the low solid solubility of Er. A co-implantation of Er and O [8,9] allowed to limit Er segregation and precipitation, owing to the formation of Er-O complexes. However, at room temperature a relatively low luminescence efficiency was obtained as a result of the strong nonradiative processes competing with the radiative Er de-excitation in c-Si. More recently, it was shown that by using a SiO 2 matrix containing Er-doped Si nanoclusters, an intense room-t...

The structural properties and the room temperature luminescence of Er2O3 thin films deposited by magnetron sputtering have been studied. In spite of the well-known high reactivity of rare earth oxides towards silicon, films characterized by good morphological properties have been obtained by using a SiO2 interlayer between the film and the silicon substrate. The evolution of the properties of the Er2O3 films due to thermal annealing processes in oxygen ambient performed at temperatures in the range of 800–1200°C has been investigated in detail. The existence of well defined annealing conditions (rapid treatments at a temperature of 1100°C or higher) allowing to avoid the occurrence of extensive chemical reactions with the oxidized substrate has been demonstrated; under these conditions, the thermal process has a beneficial effect on both structural and optical properties of the film, and an increase of the photoluminescence (PL) intensity by about a factor of 40 with respect to the as-deposited material has been observed. The enhanced efficiency of the photon emission process has been correlated with the longer lifetime of the PL signal. Finally, the conditions leading to a reaction of Er2O3 with the substrate have been also identified, and evidences about the formation of silicate-like phases have been collected.

The crystallization kinetics of as-deposited and ion implanted amorphous Ge2Sb2Te5 thin films has been measured by time resolved reflectivity. An enhancement of the crystallization process occurred in the implanted samples. Raman scattering analysis was used to correlate the stability of the amorphous phase to its structure. The variation of the Raman signal after ion irradiation is consistent with a reduction in Ge–Te tetrahedral bonds, characteristic of the Ge coordination in amorphous Ge2Sb2Te5.

High doping regimes of B implanted Ge have been accurately characterized combining Hall effect technique and nuclear reaction analysis. Preamorphized Ge was implanted with B at 35keV (spanning the 0.25–25×1020B∕cm3 concentration range) and recrystallized by solid phase epitaxy at 360°C. The Hall scattering factor and the maximum concentration of active B resulted rH=1.21 and ∼5.7×1020B∕cm3, respectively. The room-temperature carrier mobility was accurately measured, decreasing from ∼300to50cm2∕Vs in the investigated dopant density, and a fitting empirical law is given. These results allow reliable evaluation for Ge application in future microelectronic devices.

Experimental studies about electrical activation and clustering of B implanted in crystalline Ge (c-Ge) are reported. To this aim, we structurally and electrically investigated c-Ge samples implanted at different temperatures with B at 35 keV in the high-concentration dopant regime (0.67–25×1020 B/cm3). We elucidated that a high level of damage, in the form of amorphous pockets, favors the electrical activation of the dopant, and a complete activation was achieved for properly chosen implant conditions. We found, by joining channeling measurements with the electrical ones, that the reason for incomplete B activation is the formation of B-Ge complexes with a well-defined stoichiometry of 1:8. The thermal stability of the B-doped samples, up to 550 °C, was also investigated. The tested stability demonstrates that the B clustering, responsible of B inactivity, is characterized by high binding energies and higher thermal budgets are needed to make them to dissolve. These studies, besides clarify the physical mechanisms by which B dopes Ge, can be helpful for the realization of ultrashallow junctions for the future generation devices.