Nowadays, Schottky-barrier diode (SBD) on 4H-SiC is an established technology used in several real-world applications [1]. Although this large use, additional improvement is still possible for a fully exploitation of the 4H-SiC potentialities. Essentially, the properties of the metal/4H-SiC contact are at the base of the SBD performance and the achievement of a superior control on this interface drives an optimization of the use of the SBD. Over the last two decades, various approaches have been considered for gaining control in this system. Particular attention was paid to the choice of the metal and its evolution with thermal annealing in the Schottky contact formation [2,3]. Recently, the exploration of low-work function materials, such as W and Mo-based contacts, has demonstrated promising results for minimizing the power dissipation of Schottky diodes and offering good thermal stability [3,4]. In particular, Mo has demonstrated a large variability of the Schottky barrier height (ϕB) value dependently on the passivation treatment for the surface preparation [5] or the temperature of the deposition processing step [6], with the ϕB varying between 1.0 and 1.5 eV. From a structural point of view, Mo can readily form carbides and silicides and for that reason Mo-film deposited with Si or C element can be useful in preventing the reaction with SiC surface. For example, Mo-based contacts containing C were recently investigated, either deposited in laminated layers or from Mo-C alloyed targets [7,8], demonstrated stability of the electrical characteristics even at high annealing temperature. However, the origin of this electrical behavior is not clear and additional investigation is necessary to discriminate the role of the C. In this study we follow the evolution of the electrical properties of Mo/4H-SiC contacts with the increasing to the annealing temperature. The electrical characterization is combined with a microstructural analysis to shed light on the possible reaction at the nanometric scale to explain the electrical behavior. The starting material was a 4H-SiC wafer with a n-type epitaxial layer (1.5×1016 cm-3) grown onto a n+ doped substrate. Back-side Ohmic contact was fabricated by sputtering 100 nm-thick Ni layer, followed by a thermal annealing treatment at 950 °C in N2 for 60 s. Then, for the front side Schottky contact 80 nm-thick Mo film was sputtered with the contacts defined by optical photolithography and lift-off. Rapid thermal annealing treatments were performed in a furnace for 10 min in N2 at temperature of 700 and 950 °C. The electrical characterization under forward and reverse bias was carried out for a set of equivalent diodes by I-V measurements carried out in a Karl-Suss MicroTec probe station equipped with a parameter analyzer. For the microstructural properties, lamellae prepared by focused ion beam (FIB) of both samples were characterized by Transmission Electronic Microscopy (TEM). A GIF Quantum ER system was also used for electron energy loss spectroscopy (EELS) measurements. The forward current density–voltage (J-V) characteristics, representative of the electrical behavior in the as-deposited and 700 and 950 °C-annealed the Mo/4H-SiC contact contacts, are plotted in Fig.1. We observed that the as-deposited and 700 °C-annealed Mo/4H-SiC contacts have similar electrical characteristics, whereas a double-barrier behavior appeared in the J-V curves of the 950 °C-annealed contact, indicating an increase of inhomogeneity of the Schottky barrier. As shown in Fig.2, up to annealing at 700 °C only a slight variation of the ϕB, from 1.45 to 1.40 eV occurred while ϕB is 1.30 eV for the 950 °C-annealed contact. The ideality factor n kept low, considering for the 950 °C-annealed sample the highest barrier part of the double-barrier J-V curve. Regarding the reverse characteristics, we observed an anomalous increase of the leakage current when the annealing temperature reached 950 °C, as shown by the representative curves of the reverse electrical behavior in Fig.3. Moreover, Fig. 4, reporting the forward J value at 0.25 V against the reverse J value at 40 V, highlighted a larger statistical distribution after annealing at 950 °C. The combined TEM analysis on the two annealed contacts (Figs. 5a and b) demonstrated a different situation occurred after 700 °C and 950 °C annealing: in the first case, an unreacted 4H-SiC surface is still present, keeping the Mo layer in the metallic form with grain sizes in the range of few tens of nanometers and providing continuous and homogeneous interface. Instead, at 950 °C we observed the presence of columnar grain in the Mo-film, therefore with a vertical size of about 75 nm. The evolution of the electrical characteristics of the Mo/4H-SiC contact revealed stable properties up to tested annealing temperature of 700 °C, while the different electrical behavior at 950°C can be explained with the different Mo/4H-SiC interface and the variation of grain size in the Mo film. Additional analyses are in progress to discriminate the role of C and possible reactions with 4H-SiC in the Mo/4H-SiC interface and highlight the current transport mechanisms. [1] F. Roccaforte et al., Microelectron. Eng. 187–188, 66 (2018). [2] R. Yakimova et al., J. Electron. Mater. 27, 871 (1998). [3] M. Vivona et al., Semicond. Sci. Technol. 37, 015012 (2022). [4] R. Rupp et al., ISPSD 2017, Sapporo, Japan 2017 pp. 355–358. [5] A. B. Renz et al., J. Appl. Phys. 127, 025704 (2020). [6] T. N. Oder and S. B. Nardella, AIP Advances 12, 025117 (2022). [7] T. Suzuki et al., IEEE Electron. Dev. Lett. 37, 618 (2016). [8] Y. Yang et al., Microelectron. Eng. 239, 111531 (2021).