ECR plasma etch fabrication of C-doped base InGaAs/InP DHBT structures:: A comparison of CH4/H2/Ar vs BCl3/N2 plasma etch chemistries

We compare ECR plasma etch fabrication of self-aligned thin emitter carbon-doped base InGaAs/InP DHBT structures using either CH4/H-2/Ar or BCl3/N-2 etch chemistries. Detrimental hydrogen passivation of the carbon doping in the base region of our structure during CH4/H-2/Ar dry etching of the emitter region is observed. Initial conductivity is not recovered with annealing up to a temperature of 500 degrees C. This passivation is not due to damage from the dry etching or from the MOMBE growth process, since DHBT structures which are ECR plasma etched in BCl3/N-2 have the same electrical characteristics as wet etched controls. It is due to hydrogen implantation from the plasma exposure. This is supported with secondary ion mass spectroscopy profiles of structures which are etched in CH4/D-2/Ar showing an accumulation of deuterium in the C-doped base region.