Transmission cathodoluminescence: A new SEM technique to study defects in bulk semiconductor samples

We report a new method of defect electron microscopy which is an extension of the well-known method of cathodoluminescence. In this new technique, which we call transmission cathodoluminescence, the luminescence generated at the top surface of a thick semiconductor sample by the electron beam of a scanning electron microscope (SEM) is used to probe the sample volume beneath the luminescing region. The intensity of the transmitted luminescence collected by a small solid-state detector mounted beneath the sample is displayed on the cathode ray tube of the SEM. We demonstrate the usefulness of this technique by imaging dislocations in GaAs substrates and GaAlAs epitaxial layers.