Energy-filtered imaging in a scanning electron microscope for dopant contrast in InP

We demonstrate that energy-filtered secondary electron (SE) imaging can be used effectively to observe dopant contrast from an InP surface covered with a contamination layer formed by continuous electron irradiation. Although dopant contrast from a surface covered with a contamination layer was almost invisible in a normal SE image, it was still clearly seen in the energy-filtered image. The contrast mechanism is explained in terms of a metal-semiconductor contact charging model and energy shift between the SE distributions across p-type and n-type regions. The results suggest that energy-filtered imaging can reduce the effects of a contamination layer.