Ohmic contacts to gallium nitride materials

A comprehensive study of the mechanisms of Ohmic contact formation on GaN–based materials has been addressed. The optimal metallization schemes and processing conditions to obtain low resistance Ohmic contacts have been investigated, discussing the role of the single metals composing the stack and the modification induced by the thermal annealing, either on the metal layers or at the interface with GaN. Physical insights on the mechanism of Ohmic contact formation have been gained by correlating the temperature dependence of the electrical parameters with a morphological/structural analysis of the interface. In the case of the AlGaN/GaN systems, the influence of the heterostructure parameters on the Ohmic contacts has been taken into account adapting the classical thermionic field emission model to the presence of the two–dimensional electron gas. Finally, the “Au-free” metallization to AlGaN/GaN heterostructures has been deeply investigated, being this latter a relevant topic for the integration of GaN technology on large scale silicon devices fabrication.

Contact person: Giuseppe Greco, IMM Catania