High-Permittivity Dielectric Stack on Gallium Nitride Formed by Silane Surface Passivation and Metal–Organic Chemical Vapor Deposition

We report the first demonstration of an in situ surface-passivation technology for a GaN substrate using vacuum anneal (VA) and silane ( SiH₄) treatment in a metal-organic chemical vapor deposition multichamber tool. Excellent electrical properties were obtained for TaN/HfAlO/GaN capacitors. Interface state density D_it was measured from midgap to near-conduction-band edge (E_C) using the conductance method at high temperatures, and the lowest D_it of 1 ?? 10¹¹ cm^-2 ?? eV^-1 at the midgap was achieved. Multiple frequency capacitance-voltage (C-V) measurement (10, 400, and 500 kHz) showed little frequency dispersion. Furthermore, the TaN/HfAlO/GaN stack was studied using high-resolution transmission electron microscopy, and the effectiveness of passivation using VA and SiH₄ was evaluated using high-resolution X-ray photoelectron spectroscopy. The method reported here effectively removes the native oxide and passivates the GaN surface during the high-k dielectric-deposition process.