Defining the safe operating area for HBTs with an InGaP emitter across temperature and current density

Statistical methods are applied for determination of the safe operating area (SOA) of HBTs across temperature and current density in terms of the FIT rate. Black’s equation is employed to predict the MTTF and likelihood methods are used to obtain the parameter estimates. Confidence intervals on the FIT rate are determined by two different methods and good agreement between the two techniques is observed. The final product of this analysis is a reliability “map” that allows the engineer to make trade-offs between current density and junction temperature when designing to a given reliability level.