Carrier activation and mobility of boron-dopant atoms in ion-implanted diamond as a function of implantation conditions

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Abstract
Natural type-IIa diamonds were implanted with either boron alone, carbon alone, or carbon plus boron at 77, 300, or 800 K. van der Pauw resistivity and Hall effect measurements of carrier concentration and mobility were made as a function of temperature to determine the most effective implantation conditions for semiconducting device applications. No measurable dopant incorporation occurs for the 800-K implant. The highest carrier concentration and mobility are observed when the implantation is carried out at 77 K. It is further shown that a significant increase in the hole concentration occurs when carbon is implanted prior to boron. These measurements provide direct confirmation of the theoretical predictions of Prins and co-workers. It is shown, however, that the carbon co-implant results in a decreased hole mobility. A multiple-step, low-temperature boron-ion implantation procedure that used three different implantation energies to produce an approximately uniformly doped p-type layer of about 200 nm thickness (as verified by secondary-ion-mass spectrometry on a separate sample) produced the best combination of carrier concentration and mobility. The resulting doped layer was used in the fabrication of an insulated-gate field-effect transistor that demonstrated current saturation and pinch-off at room temperature.