Theory of the negative photoconductivity in crossed fields

The photocurrent in crossed fields is characterized by the feedback of the transverse ambipolar drift of the excess carriers on the particle velocities in the longitudinal direction. In extrinsic semiconductors this reduction of the particle velocities may cause a negative photocurrent which is here discussed for the case of low plasma densities considering the influence of the ambipolar particle motions, the diffusion currents, the surface recombination, the bulk lifetime, the sample thickness, and the physical magnetoresistance. Numerical calculations were performed forn-InSb at 85 K.