Abstract: The structures of base semiconductor materials such as Si are modified by the use of isotope transmutation alloying. A radioisotope such as Si31 is added into a base semiconductor material such as Si, and the radioisotope is transformed to a transmuted form within the crystal lattice structure of the base semiconductor material. A master alloy comprising a relatively large amount of radioisotope such as Si31 may initially be made, followed by introduction of the master alloy into the base semiconductor material. When Si31 is used as the radioisotope, it may be transmuted into P31 within an Si crystal lattice structure. Metastable semiconductor materials doped with otherwise insoluble amounts of selected dopants are produced as a result of the transmutation process.