Abstract: A high frequency, e.g. millimeter wave, semiconductor diode structure includes a buried layer of n.sup.+ -type material and a surface layer of lightly doped n-type material on which a Schottky barrier contact is disposed. The n.sup.+ -type layer provides a low series resistance thus permitting high frequency operation. The structure is compatible with MESFET processing techniques and may thus be incorporated in an integrated circuit.

Abstract: Ions are selectively implanted into layers of a semiconductor substrate of, for example, semi-insulating gallium arsenide via a photoresist implantation mask and a metallic layer of, for example, titanium, disposed between the substrate surface and the photoresist mask. After implantation the mask and metallic layer are removed and the substrate heat treated for annealing purposes. The metallic layer acts as a buffer layer and prevents possible contamination of the substrate surface, by photoresist residues, at the annealing stage. Such contamination adversely affects the electrical properties of the substrate surface, particularly gallium arsenide substrates.