Abstract

New approaches towards high reliable thermal stable ohmic and Schottky contacts for GaN/AlGaN-HFETs have been developed and implemented in device structures. The contact technology has been systematically optimized towards i) good electrical properties, ii) superior contact morphology and contour definition and Hi) high reliability and thermal stability. HFETs employing source/drain contacts based on WSiN diffusion barriers sandwiched between an Ti/Al/Ti/Au internal layer system and an overlayer metal as well as WSiN/Au and Ir/Au gate contacts have demonstrated long term stability at 400°C, Even after temperature storage tests at 500°C no significant device degradation could be detected. Ir/Au Schottky gates have found to be stable at the rather high level of Schottky barrier height of about 1.1 eV resulting in dramatically reduced leakage currents as compared to standard Pt/Ti/Au gate contacts to GaN-HFETs.