GaAs MESFET lifetime prediction using microwave waveform probing

GaAs MESFET lifetime under Class B operation at 2 GHZ limited by hot-electron-induced degradation was accurately predicted by using a novel microwave waveform probing technique. The degradation is caused by MESFET operation in the high drain-gate voltage region and follows a square-root time dependence. To determine MESFET lifetime, instantaneous drain-gate voltage waveform is first measured at the device plane. Based on the correlation between dc and RF breakdown, the equivalent amount of dc gate current stress is then evaluated. Finally, MESFET lifetime is determined from the results of dc stressing at various gate current levels. The average gate current was found to serve as a good indicator of Class B electrical stress. Gate current-lifetime (stress)×(time) product of 1.3 A·hr/cm accurately described the MESFET technology under investigation. The lifetime prediction method can be applied to MESFET operation under any bias, drive and match conditions of interest and included into CAD programs for simulation of performance-reliability trade-offs.