Ultra accurate measurements of interface parameters with free-electron laser

We used optical pumping by the Vanderbilt free-electron laser (FEL) and the technique of internal photoemission (IPE) to measure with an accuracy of nearly 5 meV the conduction-band discontinuity of semiconductor heterojunction interfaces as GaAlAsGaAs and GeGaAs. Very recently we demonstrated, using a titanium-sapphire pumped laser, that spatially resolved internal photoemission measurements could be performed on a Ptn-GaP Schottky barrier by a scanning near-field optics microscope within a spatial resolution of 100 nm. Shear-force and photocurrent X-Y images at different photon energies enable us to map the topography and the Schottky barrier height on the same surface. The topographyʹs images, compared with the internal photoemission images, revealed zones where the morphology of the metallic layer was homogeneous, whereas the photocurrent was varying from place to place. Both results opened the possibility of measuring, in a simple and direct way, the local interface properties of real devices. A novel technique with submicrometric spatial resolution could be implemented: the spatially analyzed FEL-IPE (SAN FEL-IPE).