LOCAL INVESTIGATION OF RECOMBINATION AT GRAIN-BOUNDARIES IN SILICON BY GRAIN BOUNDARY-ELECTRON BEAM-INDUCED CURRENT

Grain boundary-electron beam induced current (GB-EBIC) is an alternati ve EBIC geometry without a Schottky contact or pn junction but with oh mic contacts on either side of a GB. The GB itself acts as a charge co llecting plane. We developed this EBIC mode both experimentally and th eoretically. We calculated the current profiles with the diffusion len gth and the recombination velocities of the GB and the surface as para meters by solving the three-dimensional diffusion problem. The influen ce of different diffusion lengths at both sides and the angle between GB and surface is discussed. By variation of the injection level and a pplication of an external bias local current voltage characteristics o f the GB are obtained from which change of the local barrier height wi th increasing injection level can be deduced. We can describe the meas ured recombination behavior by an electronic GB model with a double de pletion layer and deep interface states in a detailed balance approach . We applied this EBIC mode to grain boundaries in solar cell silicon and observed significant variations of the local recombination behavio r and the diffusion length along a single GB.