A NEW ANALYTICAL MODEL FOR CATHODOLUMINESCENCE EMISSION AS A FUNCTIONOF THE BEAM ENERGY IN GAAS AND INP MATERIALS

Starting from an analytical expression of the energy loss as a functio n of the depth, a complete analytical calculation has been done for th e cathodoluminescence (CL) intensity in GaAs and InP materials. For th e case of a bulk substrate, the analytical expression of the CL intens ity depends on the parameters of the bulk semiconductor (diffusion len gth of the minority carriers, absorption coefficient of the emitted li ght) and of the surface recombination velocity. By varying the electro n beam energy, the generation of carriers is changed in depth and the variation of the CL intensity allows the determination of the semicond uctor and surface parameters. For the case of a substrate with a top l ayer of the same material, but with a different diffusion length and a different quantum yield, a complete analytical expression of the CL i ntensity can be obtained. The variation of the CL intensity as a funct ion of the beam energy allows the determination of the parameters of t he substrate and of the top layer, as well as the quantum yield ratio between the top layer and the substrate. Application examples are show n for both cases.