Passivation study for In/sub 0.4/AlAs/In/sub 0.65/GaAs HEMTs by UHV RPECVD grown SiN/sub x/ dielectrics and their impact on I-V kink and low-frequency dispersion phenomena

The influence of silicon nitride (SiN/sub x/) passivation on the DC and low-frequency transconductance dispersion behaviours of In/sub 0.4/AIAs/In/sub 0.65/GaAs 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/sub on/) and breakdown voltage (BV/sub gd/) due to low Schottky barrier height (SBH) of InP layer. To resolve this problem, we have developed innovative SiN/sub 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/sub x/ passivation process, the DC I-V kink and the low-frequency transconductance dispersion could be significantly improved.