Conductivity conversion of N-doped diamond by additional B ion implantation

We report the first successful formation of inversion doping in diamond achieved by ion implantation, realizing conductivity conversion from n-type to p-type. Type Ib diamond containing nitrogen donors (∼3.3 × 1019 cm−3) was implanted with boron ions at multiple energies (5–200 keV) to achieve a uniform depth profile up to ∼400 nm. The implantation was performed with boron concentrations ranging from 2 × 1019 to 3.5 × 1020 cm−3, followed by high-temperature annealing. Electrical characterization revealed a transition from n-type to p-type conduction as the boron concentration exceeded the nitrogen donor level in the substrate. The heavily implanted sample (3.5 × 1020 cm−3) exhibited p-type behavior with a sheet resistance of 4 × 104Ω/□ at room temperature and an activation energy of 0.06 eV. This achievement represents the first demonstration of the conduction-type inversion in diamond by ion implantation, establishing a viable approach to locally form p-n junctions in the n-well region. The ability to locally form p-type regions within a nitrogen-rich diamond provides a decisive step toward complementary diamond transistor devices, proving that ion implantation doping is a practical and controllable method for realizing various diamond devices.