Disclosed herein is a new and improved system and method for fabricating monolithically integrated diamond semiconductor. The method may include the steps of seeding the surface of a substrate material, forming a diamond layer upon the surface of the substrate material; and forming a semiconductor layer within the diamond layer, wherein the diamond semiconductor of the semiconductor layer has n-type donor atoms and a diamond lattice, wherein the donor atoms contribute conduction electrons with mobility greater than 770 cm2/Vs to the diamond lattice at 100 kPa and 300K, and wherein the n-type donor atoms are introduced to the lattice through ion tracks.