Investigation of short-term current gain stability of GaInP/GaAs-HBTs grown by MOVPE

Abstract

Initial current gain variation in GaInP/GaAs-HBTs stressed at high-current density was investigated in dependence on base–dopant concentration and hydrogen passivation. It is shown that current-induced acceptor activation results in short-term current gain reduction, but does not affect emitter–base heterojunction properties. The incorporation of hydrogen during growth and the resulting passivation of carbon acceptors in the base layer depends mainly on carbon doping level and the precursors present during growth and cool-down. Under the growth conditions used, in-diffusion of hydrogen within AsH 3-rich growth steps turned out to be the major source of base–dopant passivation. Utilizing the blocking effect of n-type layers for H + in-diffusion we were able to reduce the base passivation ratio [H]/[C] to 0.1 leading to significant improvements in gain stability. It is shown that current gain instabilities can be completely suppressed by using a high-current density pre-stress treatment.