Improvements in or relating to semiconductor devices

A process for manufacturing gallium arsenide devices is described in which regions of high resistivity are created in the gallium arsenide by subjecting the regions to bombardment by protons and then by deuterons, the energies of the protons and deuterons being so chosen that they penetrate to the same depth. To provide a uniform resistivity throughout the depth of the treated region both bombardments are effected at a constant beam current with the particle energy increased in regular steps. (author)