No abstract

High-quality Ir/n-Si Schottky diodes have been prepared. The diodes exhibit ideal behavior at room temperature according to thermionic emission theory with linear log (I)–Vcharacteristics over eight current decades. Ideality factors less than 1.02 were obtained. Schottky barrier heights determined by forward I–V and C–V characterization are close to 0.9 eV. Current–voltage characteristics show deviations from the simple thermionic emission law at low temperature. This anomalous behavior is explained in terms of spatial inhomogeneities in the barrier height that result from the presence of a polycrystalline interlayer at the metal–semiconductor interface. The flat-band Schottky barrier height (0.98 eV) at 0 K and the temperature coefficient of the barrier (−3.8×10−4 V K−1) agree with those reported for the IrSi phase implying that some reaction between Ir and Si has taken place.

The silicidation of iridium layers by rapid thermal annealing as a function of temperature and processing time is studied for both vacuum and argon atmosphere. The electrical properties of the resulting IrSi/n-type Si diodes are determined and related to the interface properties. I -V -T spectroscopy allows us to detect interface modifications even in the case where other diagnostics cannot be employed. Rapid thermal annealing ͑RTA͒ vacuum annealed diodes show inhomogeneous potential distribution at the metal-semiconductor interface. This is related with the coexistence of different metallurgical phases ͑Ir, IrSi, and IrSi 1.75 ) at the interface as a consequence of the thermal treatments. The estimated value for the Schottky barrier height of the IrSi 1.75 is 0.7 eV. In contrast, RTA argon annealed diodes show more reproducible characteristics. The main effect of the reaction atmosphere is to slow down the reaction rate as well as to inhibit the IrSi 1.75 formation. This could be related with the residual oxygen contents of the reaction atmosphere. RTA argon annealing at 500°C during 5 min is a reliable procedure for homogeneous IrSi infrared Schottky barrier detectors fabrication that can be employed in an industrial environment.

In this article we analyze the effect of the in situ thermal treatments on the properties of the Ir/ n-type Si ͑111͒ Schottky contacts. The samples were annealed in the evaporation system at 400°C for 15 min and at 450°C for 15 min or 2 h. Rutherford backscattering spectroscopy spectra and secondary ion mass spectroscopy compositional profiles indicate that as result of the different thermal treatments performed in the samples there is a clear diffusion of silicon into the iridium layer but the composition of the metal-semiconductor interface cannot be determined. It has been shown previously that a small quantity of IrSi can be formed at an Ir-Si interface when Ir layers are deposited on Si. The current-voltage-temperature ͑I-V-T͒ behavior of these diodes indicates that it is dominated by the effect of spatial fluctuations of the surface barrier. After the thermal treatment at 400°C for 15 min the diodes show I-V characteristics that can be perfectly justified by the unidimensional model of the thermionic emission theory. The Schottky barrier value at 0 K ͑0.92 eV͒ and the temperature coefficient of the barrier ͑3•10 Ϫ4 V/K͒ corresponds with that previously reported for the IrSi. When the annealing temperature is raised to 450°C, the resulting devices show a nonhomogeneous barrier with similar values to those found at room temperature. Increasing the annealing time to 2 h leads to devices showing an increase in the ideality factor value ͑1.12͒, along with a barrier height value at room temperature ͑0.86 eV͒ which coincides with that previously reported for the IrSi 1.75 . The 0 K barrier height ͑0.72 eV͒ indicates that a phase transformation at the interface has taken place.

No abstract