The effects of (NH4)(2)S-x treatment on n-GaN MOS device with nano-laminated ALD HfAlOx and Ru gate stack

Abstract

The effects of ammonium poly-sulfide, (NH4)(2)S-x, treatment on the surface of GaN metal oxide semiconductor (MOS) device with nano-laminated atomic layer deposition (ALD) HfAlOx gate dielectric and Ru gate electrode were investigated and compared with HCl pre-treatment. Compared with sample without sulfur (S) passivation, S-passivated sample shows improved surface roughness, increased capacitance, higher breakdown voltage, smaller frequency dependence, lower interface state density (D-it). It is found that (NH4)(2)S-x can remove native oxide and passivate the surface and interface states. Surface oxidation is suppressed due to higher strength in the N-S bonds than that of the N-O bonds. Further improvement is observed with increasing (NH4)(2)S-x treatment time.