Electrical and structural properties of surfaces and interfaces in Ti/Al/Ni Ohmic contacts to p-type implanted 4H-SiC

In this work, the electrical and structural properties of Ti/Al/Ni Ohmic contacts to p-type implanted silicon carbide (4H-SiC) were studied employing different techniques. With increasing the annealing temperature, an improvement of the electrical properties of the contacts is highlighted, until an Ohmic behavior is obtained at 950 degrees C, with a specific contact resistance rho(c) = 2.3 x 10(-4) Omega cm(2). A considerable intermixing of the metal layers occurred upon annealing, as a consequence of the formation of different phases, both in the uppermost part of the stack (mainly Al3Ni2) and at the interface with SiC, where the formation of preferentially aligned TiC is observed. The formation of an Ohmic contact was associated with the occurrence of the reaction and the disorder at the interface, where the current transport is dominated by the thermionic field emission mechanism with a barrier height of 0.56 eV. (C) 2017 Elsevier B.V. All rights reserved.