The influence of the illumination direction on the field distribution in high-resistivity metal-semiconductor structures

Abstract

The dependence of the field distribution on the illumination intensity in a heavily biased high-resistivity metal-semiconductor structure exposed to intrinsic-absorption monochromatic light was investigated. The distinctions in the field distribution under illumination from the anode and cathode sides are revealed. In the bulk, these distinctions are caused by a difference in the photocarrier mobility, whereas near the surface they are caused by the different directions of diffusion and drift flows for more mobile electrons. It is demonstrated that if the cathode is illuminated, the field distribution is nonuniform. In this case, the field decreases in a thin layer with a distance from the illuminated cathode, passes through a minimum, and increases toward the anode. With increasing illumination intensity, the quasi-neutral region in the vicinity of the field minimum expands toward the anode and the lowest field decreases. On the other hand, near the illuminated cathode, the field increases for low intensities and decreases for high intensities. For sufficiently high illumination intensities, the field dependence on the coordinate in the bulk of pure crystals as a function of the distance from the illuminated electrode is independent of the illumination direction.