ELECTRON INJECTION EFFECT ON FORMATION AND DECOMPOSITION OF C-H COMPLEXES IN C-DOPED GAAS BASE OF H-IMPLANTED INGAP()GAAS HBTS/

We observed the current gain and turn-on voltage variations in H+-impl anted 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 increa se and a turn-on voltage decrease, and the second by a current gain de crease and a turn-on voltage increase. The first variation is attribut ed 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 fr om 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 i s diffused from the H+-implanted region predominantly during the HBT f abrication process. Both the formation and the decomposition of C-H co mplexes are assisted by current injection. The formation of C-H comple xes may be enhanced by the energy transfer from 2 electrons. The decom position of C-H complexes is dominated by the capturing of single elec trons. After the variation, hydrogen do not cause ''essential'' degrad ation. Consequently, the HBTs must be finally free from hydrogen. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.