Cathodoluminescence measurements on heavily boron doped homoepitaxial diamond films and their interfaces with their Ib substrates

Abstract Heavily boron doped 1.8 to 2.4 µm thick homoepitaxial diamond films with 1.5 × 10²¹ cm^–3 ≤ [B] ≤ 1.75 × 10²¹ cm^–3 have been deposited directly on their (100) Ib substrates at 830 °C. Their cathodoluminescence spectra probe the controlled thicknesses from 0.28 to 2.8 µm, therefore the bulk of the films as well as their interfaces with their substrates. The bulk of these films exhibit a band with shoulders ascribed to BE^TO (5.036 eV), FE^TO (5.094 eV) and BE^NP (5.184 eV) excitons whose energies are downward shifted by about 180 meV in comparison with monocrystalline diamond with low [B] < 5 × 10¹⁸ cm^–3. This large shift allows the appearance of narrow peaks around 5.216, 5.271 and 5.357 eV ascribed to BE^TO, FE^TO and BE^NP from interfacial layers with low [B]. From their BE^TO to FE^TO ratio, their concentration of boron on isolated substitutional sites is significantly lower than their total low [B] content measured by SIMS. A tentative model is proposed to explain the characteristics of these 40 to 160 quasihomogeneous interfacial layers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)