Hydrogen in Monocrystalline CVD Boron Doped Diamond

Abstract

The diffusion properties of hydrogen have been investigated in homoepitaxial layers of CVD boron doped diamond as a function of the diffusion temperature, the boron dopant concentration and the nature of the hydrogen source (rf or microwave plasma). Preliminary hydrogen effusion experiments on these hydrogenated samples are also reported. For both kinds of plasma we show that, below diffusion temperatures of 500 °C, the hydrogen diffusion is limited by trapping on boron acceptors. The onset of dissociation of B, H pairs occurs at 550 °C which implies a significantly higher stability of these pairs in diamond compared to silicon. However, a higher hydrogen diffusion activation energy is found in the microwave plasma exposed samples compared with the rf plasma exposed samples together with the absence of the subsurface hydrogen accumulation layer which is observed after rf plasma. Hydrogen effusion experiments show that in the rf plasma exposed samples the main effusion peak at 720 °C is attributed to the subsurface hydrogen accumulation layer. Another effusion peak at 850 °C is ascribed to the desorption of hydrogen adsorbed at the surface.