AlGaAs/GaAs HBT reliability: dependence on material and correlation to baseband noise

The long-term reliability of an AlGaAs/GaAs HBT was found to have a strong dependence on the starting epitaxial material. The measured and extrapolated lifetimes ranged from 10/sup 2/ to 10/sup 9/ hours with devices fabricated on wafers obtained from 3 different vendors. The low frequency baseband noise characteristics were used to identify the source and the nature of mechanisms that lead to current gain degradation.