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Erlangen, Germany

Ouennoughi Z.,Laboratoire Optoelectronique et Composants | Toumi S.,FIIS | Weiss R.,Laboratoire Optoelectronique et Composants
Physica B: Condensed Matter | Year: 2014

In the present work we investigate the forward current-voltage (I-V) characteristics, over a wide temperature range 298-498 K, of Mo/4H-SiC Schottky diode for which aluminum ion implantation was used to create the high resistivity layer forming the guard ring. The (I-V) analysis based on Thermionic Emission (TE) theory shows a decrease of the barrier height φBand an increase of the ideality factor n when the temperature decreases. These anomalies are mainly due to the barrier height inhomogeneities at the metal/semiconductor interface as we get a Gaussian distribution of the barrier heights when we plot the apparent barrier height φapversus q/2kT. The mean barrier height and the standard deviation obtained values are φ¯B0=1.160 eV and σ0=88.049 mV, respectively. However, by means of the modified Richardson plot Ln(Is/T2)-(q2σ02/2k2T2) versus q/kT, the mean barrier height and the Richardson constant values obtained are φ¯B0=1.139 eV and A∗=129.425 A/cm2K2, respectively. The latter value of φ¯B0matches very well with the mean barrier height obtained from the plot of φapversus q/2kT. The Richardson constant is much closer to the theoretical value of 146 A/cm2K2. The series resistance Rsis also estimated from the forward current-voltage characteristics of Mo/4H-SiC Schottky contact. This parameter shows strong temperature dependence. The T0effect is validated for the 298-498 K temperature range for the used Schottky diode and provides a clear evidence for the barrier inhomogeneity at the Mo/4H-SiC interface. Finally, we note the impact of the implantation process as well as the choice of the used ion on the characterized parameters of the Schottky contact. © 2014 Elsevier B.V. Source


Latreche A.,Laboratoire Optoelectronique et Composants | Ouennoughi Z.,Laboratoire Optoelectronique et Composants | Sellai A.,Sultan Qaboos University | Weiss R.,FIIS | Ryssel H.,FIIS
Semiconductor Science and Technology | Year: 2011

The electrical characteristics of ion-implanted guard rings for molybdenum (Mo) Schottky diodes on 4H-SiC are analyzed on the basis of the standard thermionic emission model and the assumption of a Gaussian distribution of the barrier height. For edge termination, high-resistivity guard rings manufactured by carbon and aluminum ion-implanted areas were used. Extractions of barrier heights of molybdenum on silicon carbide (4H-SiC) Schottky diodes have been performed on structures with various gate metallization, using both current-voltage-temperature (I-V-T) and capacitance-voltage (C-V) measurements. Characteristic features of the Schottky barrier height (SBH) are considered in relation to the specific dose of the carbon- or aluminum-implanted guard ring. Contacts showed excellent Schottky behavior ideality factors between 1.02 and 1.24 in the range of 303-473 K. The measured SBHs were between 0.92 and 1.17 eV in the same temperature range from I-V-T characteristics. The variations in the barrier height, which is significantly temperature- and implantation-dose- dependent, are well fitted to a single Gaussian distribution function. Experimental results agree reasonably well by using this approach, particularly for carbon implantation dose of 1.75 × 1014 cm-2, and a mean barrier height () of 1.22 eV and zero bias standard deviation σ0 = 0.067 V have been obtained. Furthermore, the modified Richardson plot according to the Gaussian distribution model resulted in a mean barrier height () and a Richardson constant (A*) of 1.22 eV and 148 A cm-2 K-2, respectively. The A* value obtained from this plot is in very close agreement with the theoretical value of 146 A cm -2 K-2 for n-type 4H-SiC. Therefore, it has been concluded that the temperature dependence of the forward (I-V) characteristics of the Mo/4H-SiC contacts can be successfully explained on the basis of a thermionic emission conduction mechanism with Guassianly distributed barriers. © 2011 IOP Publishing Ltd. Source


Boussouar L.,Laboratoire Optoelectronique et Composants | Ouennoughi Z.,Laboratoire Optoelectronique et Composants | Rouag N.,Laboratoire Optoelectronique et Composants | Sellai A.,Sultan Qaboos University | And 2 more authors.
Microelectronic Engineering | Year: 2011

Using current-voltage measurements, we have investigated the electrical behavior of molybdenum on 4H-SiC Schottky diodes of various areas and having different edge terminations consisting of high resistivity guard rings manufactured by carbon ion-implantation. Both forward and reverse electrical characteristics of Schottky contacts indicated a presence of inhomogeneities. The forward I-V characteristics have been primarily analyzed within the framework of a standard thermionic emission theory. Schottky-barrier heights and ideality factors are found to appreciably vary from diode to diode. A more general model which takes into account the inhomogeneity of the Schottky barrier has been then used to extract the parameters pertinent to the barrier height distribution. The description of the experimental results using Tung's model allowed us to determine the value of the average laterally homogeneous SBH barrier height between 1.2 and 1.39 eV for Mo/4H-SiC Schottky diodes. The patch's properties (the number of patches, the patch strength and the local series resistance) were also obtained from the fit to the experimental I-V characteristics of the current through "patchy" diodes. The obtained results are best described with this extended "pinch off" model. With respect to the reverse characteristics, the remarked absence of a non-saturating behavior as a function of bias in the experimental reverse-bias branch may well be attributed to the presence of defects and/or inhomogeneous Schottky barrier heights, associated with the non-ideal contacts. © 2010 Elsevier B.V. All rights reserved. Source

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