Determination of Nonuniform Diffusion Length and Electric Field in Semiconductors

A method is proposed that purports to measure the nonuniform diffusion length L(x) in the presence of an arbitrary electric field Ex(x). A point source of carrier generation (as a model for an electron beam) scans across the sample in the thickness direction x while the induced currents are measured at two reverse-biased junctions sandwiching the sample. L(x) and (Exnp +Dp)/Dp can be de duced from the currents. If only one collecting junction is present, one of the two functions may be deduced provided that the other is known; in addition, the surface recombination velocity at the other boundaty may be determined in the presence of arbitrary L(x) and Ex(x). With additional scanning in the y and z directions, quasi three-dimensior al mapping is possible.