Process of producing devices with photoelectrochemically produced gratings

Claim 1

A process for making a device comprising a pattern on a semiconductor surface in which said pattern is an optical grating consisting of an array of parallel lines of light with periodicity of less than 5.0 μm and is made by a procedure comprising the step of photoelectrochemically etching at least part of the surface of the semiconductor to produce oxidized species by passing current through the semiconductor, an electrolytic solution and a cathode, said electrolytic solution comprising an aqueous solution of at least one acid selected from the group consisting of HCl, HBr and H 2 SO 4 with a total acid concentration ranging from 1 to 5 molar and a conductivity greater than 0.0001 mhos/cm in which the step further comprises: a. applying a potential to the semiconductor between the maximum potential of the valence band of the semiconductor in the electrolytic solution and the minimum potential of the conduction band of the semiconductor in the electrolytic solution; b. illuminating the part of the surface of the semiconductor to be etched with radiation of sufficient energy to produce holes in the valence band; c. including in the composition of the electrolytic solution species which removes the oxidized species from the surface of the semiconductor.