The optoelectronic and structural properties of hydrogenated amorphous silicon-carbon alloys ͑a-SiC:H͒ are studied over the entire compositional range of carbon content. The films are prepared using low-power electron-cyclotron resonance ͑ECR͒ plasma-enhanced chemical vapor deposition. The carbon content was varied by using different methane ͑or ethylene-͒-to-silane gas phase ratios and by introducing the methane ͑or ethylene͒ either remotely into the plasma stream or directly through the ECR source, together with the excitation gas ͑hydrogen͒. Regardless of the deposition conditions and source gases used, the optical, structural and transport properties of the a-SiC:H alloys followed simple universal dependencies related to changes in the density of states associated with their structural disorder. The deep defect density from photothermal deflection spectroscopy, the ESR spin density, the steady state and the transient photoluminescence, the dark and photoconductivity, the temperature of the hydrogen evolution peaks and the bonding from infrared spectroscopy are correlated to the Urbach tail energy, the B factor of the Tauc plot and E 04 ͑defined as the energy at which the absorption coefficient is equal to 10 4 cm Ϫ1 ͒. Silicon-rich and carbon-rich regions with very different properties, corresponding approximately to carbon fractions below and above 0.5, respectively, can be distinguished. The properties of the ECR a-SiC:H alloys are compared with those of alloys deposited by rf glow discharge.

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Epitaxial Er-doped GaAs and Al0.5Ga0.5As films, 1.6 μm thick, grown by MBE on (100) GaAs substrates at 560°C, with Er concentrations in the range 9 × 1017 to 2 × 1020 cm−3 were studied with RBS/channeling and photoluminescence techniques. Angular scans in the <110> and <111> axial and (111) planar directions indicate that the Er atoms in GaAs are located on interstitial sites. In Al0.5Ga0.5As doped with 5 × 1019 Er cm−3, 70% of the Er atoms are on positions slightly displaced from the interstitial site, the rest presumably substitutional. In Al0.5Ga0.5As doped with 9 × 19 Er cm−3, more than 88% of the Er atoms are on substitutional sites.Photoluminescence around 1.54 μm is observed at room-temperature in Er-doped Al0.5Ga0.5As. Both the low and highly Er-doped samples show similar luminescence intensities; the luminescence lifetimes are on the order of 1 ms. The Er-doped GaAs does not show any measurable signal at room-temperature. Correlation of the luminescence data to the Er lattice location suggests that only substitutional Er in AlGaAs is in the luminescent trivalent state.

Iridium silicides formation by rapid thermal annealing (RTA) under vacuum at several temperatures in the range of 350 to 650°C has been investigated. The substrates and the silicide films were analyzed by Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES). At 350°C, no distinguishable phase was detected for 240 seconds of annealing time. At 400°C, for processing time up to 45 seconds only Ir1Si1 was formed, for longer processing time Ir1Si1.75 was formed too. At higher temperatures even for very short processing time, Ir1Si1.75 was formed. Ir, Ir1Si1 and Ir1Si1.75 were present simultaneously if the iridium film was thick enough and the processing time was long enough too. For thin iridium layers, the Ir1Si1 formed was totally converted to Ir1Si1.75, if the annealing time was long enough. Formation rates were observed to be three to five orders of magnitude faster than the reported for furnace annealing.

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