Tantalum‐Driven Interfacial Reconstruction Enables Ultra‐Low Contact Resistance in TiAlTa/Au GaN HEMTs

ABSTRACT The transformative potential of gallium nitride high electron mobility transistors (GaN HEMTs) in advancing carbon‐neutral power systems remains bottlenecked by contact resistance ( R c ) at the metal–semiconductor (M‐S) interface, a critical determinant of switching losses and frequency response. Herein, by engineering a TiAl/TiAlTa/Au metastructure, we propose a novel interface‐driven strategy employing Ta‐mediated interfacial reconstruction to achieve a record‐low R c of 0.07 Ω mm, which is two orders of magnitude lower than that of conventional Ti/Al/Ni/Au ohmic contacts. This innovation originates from expansion‐bolt‐like islands (shaped as inverted truncated pyramid—with extensive coverage and planar tops) formed during rapid thermal annealing (RTA) process, which are sufficiently dug into the two‐dimensional electron gas (2DEG) channel. Distinct from traditional thumbtack‐like morphology (resembling inverted cones), these expansion‐bolt‐like islands exhibit enhanced coverage to 2DEG channel, and planarized apex geometries that redistribute electric field, enabling 87% higher off‐state breakdown voltage. This interface‐driven strategy envisions a universal manufacturable paradigm for next‐generation ultra‐low‐loss GaN power devices.