Deep Level Spectroscopy in Homoepitaxial Diamond Films Studied from Current Transients in Schottky Junctions

The electrical response of Schottky junctions made on boron doped homoepitaxial diamond films is investigated. Current transients due to the release of holes in the valence band from deep level traps are detected and analysed. The homoepitaxial layers grown by microwave plasma decomposition of a very small percentage of B2H6 mixed with CH4 in hydrogen receive ohmic Mo2C contacts. Rectifying contacts are achieved either with aluminium or erbium after suitable pre- and post-treatments. A rectifying ratio of three orders of magnitude can persist up to 500 °C and makes deep level transient spectroscopy (DLTS) possible. A deep level at (1.30 ± 0.10) eV above the valence band is detected and seems to be common to various diamond crystals. Another deep level at (1.14 ± 0.05) eV above the valence band exists only if an oxygen plasma treatment is applied to the sample before the Schottky contact deposition. Thermal capture cross-sections are also deduced.