Reliability implication of InGaP HBT emitter ledge dimension

Summary form only given. GaAs-based HBT reliability is determined by many factors including device layout design, epi-material properties and device fabrication processes. The latest generation of device designs across the industry almost without exception utilize an emitter passivation ledge to minimize base epi-layer surface recombination component of the base current. We have established a direct experimental correlation between physically measured ledge coverage and base current ideality factor extracted from electrical measurements. Degraded devices typically show increased ideality factors. A higher ideality factor, however, does not necessarily mean faster degradation. The implication for device reliability is discussed.