Gap States and ESR of Boron-Doped CVD Amorphous Silicon

The density distribution of the gap states in boron-doped CVD amorphous silicon has been determined by the field-effect technique. The measured density of the midgap states as high as 2×10 18 cm -3 eV -1 for undoped a-Si is appreciably reduced by doping with boron atoms. Electronic states arising from unpaired spins are found at energies near E v +0.30 eV, creating a bump in the gap states. The experimental results are discussed in conjunction with a divacancy model.