On possible new methods for δ-layer synthesis of the diamond transistor

Abstract

An upper estimate of the activation barrier Ea, overcome by boron atom during its adsorption on singular face of unalloyed diamond, has been obtained using quantum chemistry methods. This process is connected with the formation of boron-doped δ-layer in the unalloyed diamond, which is an integral part of the diamond transistor. The estimate of Ea was found to be approximately 6–7 eV. It is correspondent by the order of magnitude with floating electrode potential drop relative to stationary low-temperature plasma at electronic temperature above ~ 1 eV. Meanwhile, in the existing high-frequency plasma-enhanced CVD (MWCVD) technology used to create boron-doped δ-layers, the source of the δ-layer growth is high-energy boron ions with energies of hundreds of eV (and even units of keV) which enter the substrate from MW plasma. This energy that the ions acquire at the near-electrode voltage drop is clearly excessive and leads both to excessively high depth of ion penetration into the diamond and to large dispersion of this depth. This reduces the quality of the δ-layer and the transistor efficiency as a whole. At the same time, specificity of high-frequency plasma, created in the MW-resonator for the diamond growth, allows plasma modes and diamond growth both with large (units of keV) and small (units of eV) near-electrode voltage drops. This paper considers the possibility of switching between these two modes. The high-drop mode realizes the rapid growth of unalloyed diamond and the low-drop mode – high quality δ-layer.