Electron injection effect on formation and decomposition of C–H complexes in C-doped GaAs Base of H +-implanted InGaP/GaAs HBTs

Abstract

We observed the current gain and turn-on voltage variations in H +-implanted InGaP/GaAs heterojunction bipolar transistors with carbon-doped bases under high temperature current stresses. The variation occurs in two stages: the first stage is characterized by a current gain increase and a turn-on voltage decrease, and the second by a current gain decrease and a turn-on voltage increase. The first variation is attributed to a decrease of the hole concentration in the base, caused by the formation of C–H complexes in the base. The second variation arises from an increase of the hole concentration in the base, which is brought about by a decomposition of the C–H complexes. Hydrogen in the base is diffused from the H +-implanted region predominantly during the HBT fabrication process. Both the formation and the decomposition of C–H complexes are assisted by current injection. The formation of C–H complexes may be enhanced by the energy transfer from 2 electrons. The decomposition of C–H complexes is dominated by the capturing of single electrons. After the variation, hydrogen do not cause “essential” degradation. Consequently, the HBTs must be finally free from hydrogen.