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 (SiH
₄
+ NH
₃
) or silane (SiH
₄
) 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 SiH
₄
+ NH
₃
or SiH
₄
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 × 10
¹²
cm
^-2
· eV
^-1
. This is reduced to ~4.0 × 10
¹¹
cm
^-2
· eV
^-1
and ~2.0 × 10
¹⁰
cm
^-2
· eV
^-1
for samples that received the in situ SiH
₄
+ NH
₃
treatment and in situ SiH
₄
treatment, respectively.