Reliability of GaAs PHEMT under hydrogen containing atmosphere

Degradation of PHEMTs by hydrogen was verified by DC life tests in the hermetic packages and in the forming gases containing different hydrogen concentrations. We have found that a hydrogen partial pressure in the order of 2 torr will cause Ids change by 20% in about 800 hours at 125/spl deg/C and about 300 hours at 150/spl deg/C. The signature of hydrogen degradation is a sudden and significant drain current degradation followed by some recovery. It appeared that the degradation is both temperature and H/sub 2/ partial pressure dependent. Failure analysis indicates that the degradation is localized under the gate and that the major failure mechanism is due to the effective gate voltage being modified negatively by the atomic hydrogen.