In situ Surface Passivation of Gallium Nitride for Metal–Organic Chemical Vapor Deposition of High-Permittivity Gate Dielectric

We report the demonstration of novel techniques for surface passivation of gallium nitride (GaN), comprising the steps of in situ vacuum anneal (VA) and silane-ammonia (SiH₄ + NH₃) or silane (SiH₄) treatment for GaN, prior to the formation of high-permittivity gate dielectric in a multichamber metal-organic chemical vapor deposition tool. The effects of VA temperature and the SiH₄ + NH₃ or SiH₄ treatment temperature on interface quality was investigated. High-temperature capacitance-voltage characterization was also performed to probe the interface states near the midgap of GaN. Interface state density D_it as a function of energy was extracted. Without in situ passivation, a control TaN/HfAlO/GaN capacitor has a midgap D_it of ~2.0 × 10¹² cm^-2 · eV^-1. This is reduced to ~4.0 × 10¹¹ cm^-2 · eV^-1 and ~2.0 × 10¹⁰ cm^-2 · eV^-1 for samples that received the in situ SiH₄ + NH₃ treatment and in situ SiH₄ treatment, respectively.