Recess-Etched and Tetramethylammonium Hydroxide-Treated Nanoscale Pattern on AlGaN/GaN High-Electron-Mobility-Transistors for Improved Ohmic Contact

Ohmic contacts are formed by recess etching the source and the drain regions with line and dot patterns of a few hundred nanometers on an AlGaN/GaN heterostructure and treating the surface with tetramethylammonium hydroxide (TMAH) prior to ohmic metal deposition. Electrical characterizations show that ohmic behavior is obtained at a low annealing temperature of 700 ◦ C as the direct contact area to the two-dimensional electron gas (2DEG) is increased via the etched patterns, and the ohmic contact is further improved when the interface is treated with TMAH. The analyses based on transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and atomic force microcopy confirm the presence of an improved ohmic contact interface and morphology, suggesting a novel and viable route towards the fabrication of AlGaN/GaN-based devices with improved controllability and reliability.