Screening for early and rapid degradation in GaAs/AlGaAs HBTs

We describe a series of pre-stress measurements, including optical inspection, DC parameter tests, electroluminescence, and noise measurements on GaAs/AlGaAs HBTs designed to screen out devices that suffer early failure. A bias stress test on these devices was then performed, and the correlation between lifetime of the devices and the pre-stress tests is determined, For this particular set of devices, optical inspection and electroluminescence showed the best correlation. We also describe the complicated relationship between pre- and post-stress noise characteristics in HBTs.