Reliability of Al/Ti gate AlGaAs/GaAs power HFETs in hydrogen gas

Here we approach for the first time the problem of hydrogen poisoning for Al/Ti-gate (Pt-free) AlGaAs/GaAs power HFETs. Throughout the stress, we have monitored the changes of I/sub DSS/, g/sub m/, threshold voltage (V/sub T/) and gate barrier height (/spl Phi//sub B/) The separate measurement of the shifts of V/sub T/ and /spl Phi//sub B/ allows us to gain new insight of the mechanisms underlying the device changes during hydrogen exposure. Moreover, by measuring the source-gate and drain-gate breakdown voltages, as well as the g/sub m/ frequency dispersion, we can speculate on the effect of hydrogenation on the access regions on the gate sides.