Interface properties and capacitance-voltage behaviour of diamond devices prepared by microwave-assisted CVD

Free standing diamond films were used to study the effect of diamond surfac e morphology and microstructure on the electrical properties of Schottky ba rrier diodes. By using free standing films both the rough top diamond surfa ce and the very smooth bottom surface are available for post-metal depositi on. Rectifying electrical contacts were then established either with the sm ooth or the rough surface. The estimate of doping density from the capacita nce-voltage plots shows that the smooth surface has a lower doping density when compared with the top layers of the same film. The results also show t hat surface roughness does not contribute significantly to the frequency di spersion of the small signal capacitance. The electrical properties of an a brupt asymmetric n(+)(silicon)-p(diamond) junction have also been measured. The I-V curves exhibit at low temperatures a plateau near zero bias, and s how inversion of rectification. Capacitance-voltage characteristics show a capacitance minimum with forward bias, which is dependent on the environmen t conditions. It is proposed that this anomalous effect arises from high le vel injection of minority carriers into the bulk.