Passivation study for In0.4AlAs/In0.65GaAs HEMTs by UHV RPECVD grown SiNx dielectrics and their impact on I-V kink and low-frequency dispersion phenomena

The influence of silicon nitride (SiN_x) passivation on the DC and low-frequency transconductance dispersion behaviours of In_0.4AIAs/In_0.65GaAs HEMTs has been investigated. Although the surface passivation using MBE grown thin InP etch-stop is effective to suppress I-V kink phenomena, it has critical drawbacks of large gate leakage current, low gate turn-on (V_on) and breakdown voltage (BV_gd) due to low Schottky barrier height (SBH) of InP layer. To resolve this problem, we have developed innovative SiN_x passivation process to prevent I-V kink as well as to maintain low gate leakage current by UHV remote-PECVD system. Through the optimized SiN_x passivation process, the DC I-V kink and the low-frequency transconductance dispersion could be significantly improved.