Reliability investigation of InGaP/GaAs heterojunction bipolar transistors

During elevated-temperature bias stress, InGaP/GaAs HBT's grown by MOCVD show a medium-term degradation in current gain of about 20%, with an activation energy of 0.64 eV. They also show a corresponding decrease in base resistance and an increase in turn-on voltage. InGaP/GaAs HBTs grown by GSMBE, however, do not show this degradation. SIMS measurements show a five times greater than GSMBE-epi hydrogen concentration of about 10/sup 19/ cm/sup -3/ in the base layer of the MOCVD-grown epi. The degradation can be explained by acceptor depassivation due to hydrogen out-diffusion from the epi during stress.