A novel, nondestructive, technique using EBIC to determine diffusion lengths in GaAs solar cells

A nondestructive technique for measuring minority carrier diffusion lengths in GaAs and other single crystal solar cells is described. The technique relies on the measurement of EBIC (electron beam induced current) from a cell. As the primary beam voltage is varied, the penetration depth of the beam changes. Using a Monte-Carlo simulation of the carrier generation produced by the beam, and solving the minority carrier continuity equation, one can model the current collection. Adjusting the diffusion lengths used in the model, to fit the experimental data, one can determine, with good accuracy, diffusion lengths in the actual device. The technique has been applied to as-made and irradiated cells and used to determine material degradation coefficients.