A comparative study of the I-V characteristics of diodes fabricated on as-grown and thermochemically polished CVD diamond films

Energies ranging between 24 and 50 keV, inclusively, are used for boron ion implantation of as-grown and thermochemically polished CVD diamond films at a total dose of 1E16 cm-2 in order to achieve p-type conductivity. N-type conductivity is acquired by lithium ion implantation of the films by a single energy of 50 keV at a dose of 2E16 cm-2. Current–voltage (I–V) characteristics reveal that leakage currents of diodes fabricated on as-grown films are approximately 2 orders of magnitude higher that those on polished films. Moreover, currents at higher voltages as less in the diodes of as-grown films in comparison to identical diodes on the polished films. The I–V characteristics of diodes on the polished films contain the trap filling, Frenkelpole emission, thermionic emission and the space charge limited current regimes but those on the as-grown films manifest a quasi-linear behavior probably due to lateral penetration of implants in the i-regions. A reduction in current of approximately 2 orders of magnitude is observed on n–i–n structures after annealing the films at 300 °C. Onset voltages of -10 V are due to the low concentration (~1E14 cm-2 ) of nitrogen centers in the diamond films.