Hydrogen lateral diffusion by annealing at low temperature was proposed to eliminate the burn-in effect in carbon-doped InGaP/GaAs heterojunction bipolar transistors (HBTs). After a thermal annealing at 480degreesC for 30 min, the current gain variations caused by the electrical stress decreased from 42.7% to 2.6% as the emitter width was reduced from 100 to 5 pm. After the annealing process, the sheet resistance was decreased from 194.4 to 162.7 ohm/sq. as the van der Pauw line widths was reduced from 65 to 5 pm. Effective doping concentration in base layer was increased by removal of incorporated hydrogen atoms. Degradation of device characteristics was not obvious after annealing by comparing the ratio difference of current gain to base sheet resistance. (C) 2003 Elsevier Ltd. All rights reserved.