Space-charge-limited current in hydrogenated amorphous carbon films containing silicon and oxygen

Evolution of the dark room-temperature current-voltage characteristics of hydrogenated amorphous carbon films containing silicon and oxygen with deposition energy growth was investigated at applied electric fields up to 6 x 10(5) V/cm. It was shown that the character of current voltage dependences is influenced by the deposition energy, which is determined by the value of the self-bias voltage, V-sb, varied in the range from -100 to -1400 V, and is described in terms of the space-charge-limited current in the presence of bulk traps, presumably having an exponential energy distribution. In films deposited at moderate values of self-bias voltage (-400 to -800 V) the trap-filled limit mode of the Gaussian-distributed deep trap set in the electric fields 5 x 10(3)-10(5) V/cm was observed. At electric fields exceeding 3 x 10(5) V/cm, phonon-assisted tunneling through the reduced electric-field potential barrier of the trap enhances the space-charge-limited current. The absence of thermal activation of the carriers at the mobility threshold caused by the reduction in trap depth in the electric field suggests deviation of the trap potential from the Coulomb one. (C) 2002 Elsevier Science B.V. All rights reserved.