Reliability of InGaP emitter HBTs at high collector voltage

We show analytically how bipolar transistor breakdown voltage varies between BVceo and BVcbo, depending on the ratio of total emitter and base resistances (Ree/Rbb). We present lifetest results for InGaP emitter HBTs biased above Vce = BVceo while using Ree/Rbb = 1. We obtained MTTF /spl sim/ 1400 h at T/sub j/,/sub peak/ /spl ap/ 330/spl deg/C for both standard epi and a high breakdown voltage power epi. Failures are characterized by sudden /spl beta/ drift at Vce /spl lsim/ BVceo, while at higher Vce, gradual /spl beta/ drift also becomes important. We believe this is the first published lifetest study of GaAs-based HBTs stressed at high Vce. Our results further demonstrate the excellent reliability that can be achieved with InGaP-emitter HBTs.