Al based alloys, such as Ti/Al, are commonly used for ohmic contacts on p-type SiC.
The interfacial structures of a metal alloy film on SiC are very complicated after annealing. Al is
considered as the key element responsible for forming ohmic contacts on p-type SiC, and reacts
with C from SiC and forms Al4C3 and Si during annealing. In this study, we have investigated
ohmic contact formation of a single component Al4C3 film on p-type SiC. Based on the
stoichiometric formation of Al4C3 between Al and C at high temperatures, several samples with
various Al/C mole ratios have been examined for ohmic contact formation after different annealing
temperatures. Carbon rich and stoichiometric Al4C3 films form ohmic contacts on p-type 4H-SiC
(~2.8 x1018 cm-3 ) after annealing at 800 and 900°C. X-ray diffraction (XRD) data have shown that a
single component Al4C3 is formed when an ohmic contact on p-type SiC is activated. Al/SiC, as the
control sample, does not form ohmic contacts under the same conditions. This study reveals that
Al4C3 can be responsible for forming ohmic contacts on p-type SiC. However, its chemical
instability requires that the secondary metal is necessary to form stable ohmic contacts when Albased
films are used.
Ohmic Contact Formation Mechanism of Pd Nonalloyed Contacts on p-Type GaN
