Impact of Surface Passivation on the Dynamic ON-Resistance of Proton-Irradiated AlGaN/GaN HEMTs

Radiation tolerance of AlGaN/GaN high-electron mobility transistors (HEMTs) is studied with 2-MeV protons, up to a fluence of 6×10
¹⁴
H
⁺
/cm
²
(about 200 times of typical Si MOSFET rating). The increase in dynamic ON-resistance (R
_ONDYN
) after radiation is observed to be much more severe than that of static ON-resistance. Radiation-induced donorlike traps located near the two-dimensional electron gas trap electrons, which is responsible for the phenomenon. Compared with the devices passivated by conventional plasma-enhanced chemical vapor deposition (PECVD) SiN, GaN HEMTs with 10 nm of in situ SiN before the PECVD SiN step demonstrate much less increase in R
_ONDYN
from 2300% to only 300%. The in situ SiN is believed to reduce the process damage by PECVD, improving radiation tolerance.