Reliability of AlGaAs and InGaP heterojunction bipolar transistors

Heterojunction bipolar transistors (HBTs) are key devices for a variety of applications including L-band power amplifiers, high speed A/D converters, broadband amplifiers, laser drivers, and low phase noise oscillators. AlGaAs emitter HBTs have demonstrated sufficient reliability for L-band mobile phone applications. For applications which require extended reliability performance at high junction temperatures (> 250 degrees C) and large current densities (> 50 kA/cm(2)), InGaP emitter HBTs are the preferred devices. The excellent reliability of InGaP/GaAs HBTs has been confirmed at various laboratories. At a moderate current density and junction temperature, J(c) = 25 kA/cm(2) and T-j = 264 degrees C, no device failures were reported out to 10,000 hours in a sample of 10 devices. Reliability testing performed up to a junction temperature of 360 degrees C and at a higher current density (J(c) = 60 kA/cm(2)) showed an extrapolated MTTF of 5 x 10(5) hours at T-j = 150 degrees C. The activation energy for AlGaAs/GaAs HBTs was 0.57 eV, while the activation energy for InGaP/GaAs HBTs was 0.68 eV, which indicated a similar failure mechanism for both devices.