We propose two novel methods of determining nonideal Schottky and p-n junction diodes parameters from I–V plots. The series resistance Rs, saturation current Is, as well as the bias-dependent ideality factor n(V), can be obtained from two successive I–V measurements—one solely of the diode and the other with an external resistance added in series with the measured diode. Our analysis confirms that the methods produce accurate and reliable results even when the conventional techniques fail, such as when we have strongly varying function n(V) in the presence of series resistance and an experimental noise.
The properties of thin (350 Å) Ti layers deposited on Si0.89Ge0.11 layers epitaxially grown on Si(001) were studied as a function of isochronal (30 min.) thermal treatments in the temperature range Ta=550–800°C. Both as-deposited and annealed at Ta up to 750°C Schottky diodes revealed near-ideal I–V and C–V characteristics with the same flat-band barrier height eV. The results indicate that at these Ta the Fermi level is pinned with respect to the conduction band.Annealing at 800°C resulted in an improvement of the Schottky diodes quality and a drop in and the series resistance Rs of the contacts. The values of the ideality factor n and ( measured were 1.03±0.02 and 0.56±0.007 eV, correspondingly. The electrical parameters of these metal/semiconductor contacts were correlated with the dynamics of interfacial reactions due to the applied heat-treatments.
Si 1−x Ge x films (x=0.22) epitaxially grown by ion beam-sputter deposition on (001) Si substrates were subjected to rapid and conventional thermal annealings at different temperatures. Strain measurements carried out by means of high-resolution x-ray diffraction exhibited strongly nonmonotonous strain dependencies on the annealing time. We observed short-time and long-time relaxation modes with activation energies of 4.6 and 1.3 eV, respectively, and unexpectedly, an additional mode of strain recovery at intermediate time durations with an activation energy of 1.6 eV. This behavior was attributed to processes that involve {113} two-dimensional defects, i.e., agglomerates of interstitials, which were identified by means of transmission electron microscopy.
Structural properties of Si1−xGex layers epitaxially grown on Si(100) by Ion Beam Sputter Deposition were studied as a function of growth temperature and film thickness. It was shown that the structure of defects strongly depends on the growth temperature, Tg. The dislocations cross grid which is observed at the SiGe/Si interface for layers grown at high (700 °C) Tg is missing in layers grown at low (≲550 °C) Tg, while a new type of defects parallel to {001} and {113} lattice planes appear at these temperatures. The optimal Tg for a Ge content of 20-25 at. % was found to be close to 550-625 °C. Surface roughness for all the growth temperatures was found to be less than that for such a ‘‘smooth’’ technique as MBE. Photoluminescence studies revealed, to the best of our knowledge for the first time, two peaks on the low energy side in the neighborhood of the Si(TO) peak of the epilayers. The evolution of the intensity of these peaks is strongly correlated with the dynamics of strain relaxation and can be attributed to a set of dislocations at the SiGe/Si interface extending both to the epilayer and to the bulk Si.
The electrical properties of a thin ͑350 Å͒ layer deposited on a molecular beam epitaxial grown Si 0.89 Ge 0.11 /Si(001) heterostructure and subsequently annealed at T a ϭ550-800°C were studied in a wide ͑80-325 K͒ temperature range. Annealing at 800°C produces a single reaction product, the C54 phase of Ti͑SiGe͒ 2 , while lower temperature anneals result in the coexistence of a few intermetallic compounds. It was found that while for annealing temperatures lower than 800°C, the Fermi level is pinned with respect to the conduction band, annealing at 800°C results in Fermi level partial pinning with respect to the valence band. The current flow in this case is controlled mainly by thermionic emission in the presence of interface states. Two kinds of traps were observed by deep level transient spectroscopy in the barrier region after the 800°C annealing. Acceptor-like traps with an activation energy of Ϸ0.46-0.5 eV, a capture cross-section a ϭ1.3ϫ10 Ϫ12 cm 2 , and a density D t Ϸ3ϫ10 13 eV Ϫ1 cm Ϫ2 , which most likely originate from the strain relaxation in the SiGe epilayer, were found to be responsible for the partial Fermi level pinning at the interface. Electron traps with an activation energy of Ϸ0.17 eV and a capture cross-section d ϭ7.7ϫ10 Ϫ16 cm 2 were also identified and attributed to the SiGe epilayer; they are assumed to originate from a well-known vacancy-oxygen center.
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