Electrical properties of the free-standing diamond film at high voltages

Polycrystalline diamond films were deposited on p-type (100) silicon substrates by the microwave plasma chemical vapor deposition system. The free-standing diamond film was then obtained by etching the silicon substrate with a KOH solution. It was found that more non-diamond components, i.e., SiC and amorphous carbon, existed on the bottom surface of the free-standing diamond film. Two different contact geometries, coplanar contact and sandwich contact geometries, were used to characterize the in-plane and transverse high-voltage electrical properties of the free-standing diamond film, respectively. The transverse electrical property of the free-standing diamond film showed the asymmetric current-voltage (I-V) characteristic and lower breakdown voltage at -220 V and 850 V. However, the in-plane electrical property exhibited the symmetric I-V characteristic in the range of -1100 V to 1100 V. The electrical properties were successfully represented by the Frenkel-Poole conduction mechanism at high voltages (> 200 V). The simulated results indicated that the breakdown field was strongly related to the Coulombic center density of the free-standing diamond film.