Reliability assessment of small signal GaAs FETs

An assessment is presented of the reliability of small signal GaAs FETs for application in communication satellites; both Al and Au gate pad devices are assessed. The MTTF and dispersion are derived from life test data of biased devices, and failure criteria and mechanisms are discussed. The probability of success of the FET devices and their use in spacecraft receivers are examined. It is found that Al FETs have inherent failure mechanisms which are predominantly intermetallic and void growth with time and temperature that make their reliability critical for seven-year life applications. Au FETs seem to have much higher reliability.