We demonstrated that the InGaP emitter ledge passivation in InGaP/GaAs heterojunction bipolar transistor (HBT) could suppress the recombination components in I-B induced by the extrinsic base surface and the defects activated by the current stress. Similar suppression of I-B by the current stress was found in unpassivated HBT with the 2 min growth interruption at the base-emitter interface under PH3 partial pressure and we attributed this to the existence of an intermediate layer at the base-emitter interface that would improve the interface crystalline quality and reduce the recombination component of I-B induced by defects at the base-emitter edge. Unpassivated HBT with the shorter post-growth annealing in time in hydrogen atmosphere, however, showed the increase in the current gain beta with the current stress because of the burn-in effect rather than the decrease in beta due to the increase of I-B induced by defects. (c) 2006 Elsevier B.V. All rights reserved.