GENERAL RELATION BETWEEN CARRIER SPATIAL DISTRIBUTIONS AND THE GENERATION FUNCTION IN PHOTOCONDUCTORS

A Fourier transform analysis is used to derive a general formula for t he determination of the dependence of the electron and hole spatial di stribution functions on the carrier-generation function, under a small -signal nonuniform illumination of a photoconductor. The suggested pro cedure also yields general basic theorems regarding the relation betwe en any carrier-generation function and the resulting electron and hole concentration distributions in the steady state. We do not know of an y previous attempt to formulate such general theorems. In particular, we prove that in the most general case, provided the Einstein relation holds, the only carrier-generation function that can yield functional ly similar distributions for the two types of carriers is spatially si nusoidal. The present results explain well the uniqueness of the sinus oidal generation function and provide the rigorous basis for the recen tly suggested photocarrier grating method, which is used for the exper imental determination of the ambipolar diffusion length in photoconduc tors.