Overview

In this chapter, the most significant results obtained in the last decade in the field of ohmic contacts to SiC are reviewed.

First, the basic concepts related to the physics of ohmic contacts and to the contact resistance measurement techniques are briefly reported.

Then, some aspects concerning the formation of low resistance (10 ^-5-10 ^-6 ?cm ²) ohmic contacts on n-type and for p-type SiC are discussed, focusing on Ni-based and Al/Ti-based contacts.

Examples of innovative applications on practical devices are also reported, as the simultaneous formation of ohmic contacts on n- and p-type SiC for vertical power MOS devices, obtained adding Al to a standard Ni contact, and a single-metal technology for ohmic and rectifying contacts in MESFETs, using Ti or Ni without post-deposition annealing.

1 Introduction

Ohmic contacts play a very important role in the signal transfer to and from the semiconductor and the external circuitry. In particular, the resistance of the contact must be negligible with respect to that of the bulk device (the device on-resistance), since a voltage drop at the contact adds an undesired contribution to the dissipated power, thus decreasing the efficiency of the system. ^[1]

Because of its excellent properties such as a wide band gap, a high critical electric field, a high thermal conductivity and a high electron saturation velocity, silicon carbide (SiC) is one of the most prominent candidates...