Near-field photocurrent measurements on boron-implanted silicon

We report near-field photocurrent (NPC) measurements performed on three boron-implanted silicon samples characterized by different implantation doses. The images were acquired at lambda=1330 nm corresponding to a photon energy of 0.93 eV which is smaller than the silicon energy gap (E-gap=1.12 eV), representing incident radiation to which silicon is virtually transparent. The NPC images reveal the presence of boron clusters which are a consequence of B implantation and rapid thermal annealing at 1100 degreesC for 30 s. Boron clusters behave as metal clusters embedded into the silicon matrix and introduce gap states which give rise to the observed photocurrent. (C) 2002 American Institute of Physics.