RESOLUTION OF SUPERLATTICE STRUCTURES WITH BACKSCATTERED ELECTRONS IN A SCANNING ELECTRON-MICROSCOPE

The Monte Carlo simulation of electron interaction with GaAs/AlAs superlattices of variable periodicities allows the calculation of the backscattered electron contrast for different energies (E0 = 25, 12.5, 8 and 4 keV). The following main results have been obtained. The resolution of a superlattice structure achievable with backscattered electrons mainly depends on the brightness of the source: for a proper signal-to-noise ratio it is possible, apart from the size of the generation volume, to get information about the beam impact point. For a well defined periodicity of the superlattice there is an energy giving a maximum contrast. According to a simple diffusion theory of backscattered electrons, the optimal energy is the one providing a depth of complete diffusion of the order of the periodicity of the superlattice.