THE EFFECT OF PASSIVATION OF BORON DOPANTS BY HYDROGEN IN NANO-CRYSTALLINE AND MICROCRYSTALLINE SILICON FILMS

It is well known that the value of room-temperature conductivity sigma (RT) of boron-doped silicon films is one order lower than that of phos phorus-doped silicon films, when they are deposited in an identical pl asma-enhanced chemical vapour deposition system. We use surface acoust ic wave and secondary-ion mass spectrometry techniques to measure the concentration of total and electrically active boron atoms. It is show n that only 0.7% of the total amount of incorporated boron is electric ally active. This is evidence that hydrogen atoms can passivate substi tutional B-Si bonds by forming the neutral B-H-Si complex. By irradiat ing the boron-doped samples with a low-energy electron beam, the neutr al B-H-Si complex converts into electrically active B-Si bonds and the conductivity can be increased by about one order of magnitude, up to the same level as that of phosphorus-doped samples.