Papers by Author: C. Fabrizio Pirri

Abstract: In this work we studied different Schottky contacts to 4H-SiC with the aim to obtain Schottky Barrier diodes (SBDs) and Junction Barrier Schottky diodes (JBS) able to operate at high temperatures, frequencies and power densities with low power losses. Schottky contacts were fabricated using Mo and Mo/Al layers annealed up to 600 °C using a Rapid Thermal Process (RTP). A comparison with previous results obtained with Ni, Ti and Ti/Al layers annealed up to 400 °C is also proposed. The Schottky contacts were characterized by means of standard Current-Voltage (I-V) and Capacitance-Voltage (C-V) techniques. X-ray Photoelectron Spectroscopy (XPS) analyses were performed in depth profile mode in order to study the structural evolution of the interface Mo/SiC and Al/Mo during annealing treatments. Mo/Al contacts show a lower barrier height and better overall performances in forward polarization when compared to the Ti- and Ni-based contacts, and they are very promising for Schottky contact fabrication on SBD and JBS.

Abstract: We have studied different Schottky and ohmic contacts on 4H-SiC with the aim to obtain Schottky barrier diodes (SBDs) capable to operate at high temperatures, frequencies and power densities for long periods of time, and showing low power losses. The control of the Schottky barrier plays an important role in minimizing the power loss of a SBD, and the metal-semiconductor interface properties strongly affect the overall performances of such a device. Schottky contacts were deposited using Ni, Ti, Ti/Al, Mo and Mo/Al layers, and the annealing treatments have been performed up to 600 °C using a rapid thermal annealing process (RTA). Ohmic contacts have been deposited on the wafer backside using Ti/Al or Ti/Ni/Ag layers. The Schottky diodes have been characterized by means of standard current-voltage (I-V) and capacitance-voltage (C-V) techniques. Schottky diodes with Mo and Mo/Al barriers show a lower barrier height and better overall performances in forward polarization when compared to the Ti- and Ni-based contacts.

Abstract: The formation of metal/diamond Ohmic contacts is essential to most electronic devices. In order to form a good Ohmic contact to diamond a carbide-forming metal such as Ti or Cr is necessary. In this study, Cr/Au contacts to heavily boron-doped single crystal CVD diamond were fabricated by subsequent deposition of Cr and Au. The surface morphology and specific contact resistance of diamond/Cr/Au contacts has been investigated. The reaction between the Cr metal and the diamond during annealing gives an improved specific contact resistance. However, this reaction also causes a significant change in the surface morphology. The surface morphology of singlecrystal diamond is shown to greatly influence the properties of metal contacts to diamond. Shearforce mode atomic force microscopy (AFM) investigations have been used to examine the diamond surface before metallization, and after removing the metal contact. The initial diamond surface was predominantly smooth, apart from some scratches from the polishing process. Surface RMS roughness values of around 0.4nm were found. Correlation between surface morphology and contact resistance has been found, with rougher surfaces exhibiting a barrier to conduction. An understanding of the contact formation process is an essential step in achieving high quality Ohmic contacts which are vital in the fabrication of high quality diamond devices.