Hydrogen Diffusion Mechanisms and Hydrogen-Dopant Interactions in Diamond

Electronic grade diamond is usually grown by Microwave Plasma assisted CVD from a hydrogen rich CH4/H2 mixture, hence hydrogen is likely to be incorporated during growth. It may thus affect the properties of the material. In this work, we present the state of the art on the understanding of the diffusion properties of hydrogen and of the hydrogen-dopant interactions in diamond. First, we show the existence of strong interactions between H and boron dopants in diamond. The formation of H-acceptor pairs results in the passivation of the acceptors. Further, we show that an excess of hydrogen in selected boron-doped diamond epitaxial layers can result in the creation of H and boron-containing donors with a ionization energy of 0.36 eV (about half the ionization energy of phosphorus). At 300 K, the n-type conductivity of hydrogenated borondoped diamond is several orders of magnitude higher than the conductivity of phosphorus-doped diamond. The formation process of these new donors is discussed.