NOVEL HIGH TEMPERATURE ANNEALED SCHOTTKY METAL FOR GaN DEVICES

We have found that Scandium metal is near ohmic as deposited on GaN , but when it is annealed at high temperatures a large barrier height Schottky forms. In this study we used Sc - Au contacts to form Schottky barrier diodes on AlGaN / GaN HEMT material. We have found that the morphology remains unchanged even after an 800 degrees centigrade anneal. This investigation has revealed that the reverse leakage current of this metal system is an order of magnitude lower than a conventional Ni - Au contact and supports a reverse breakdown that is 1/3rd larger. The similarity of the anneal temperatures to ohmic contacts enable gates and contacts to be annealed at the same time thus simplifying processing. The lack of morphology change supports the use of Sc - Au for E -beam alignment marks as well. Diode contacts on AlGaN / GaN with Schottky-ohmic separation of 10 microns demonstrated reverse breakdown in excess of 100V when the contacts were annealed at 800C. These results suggest this metallization may have applications as a new HEMT gate metal, and Schottky diodes.