Abnormal current–voltage characteristics and metal–insulator transition of amorphous carbon film/silicon heterojunction

The amorphous carbon film/n-Si (a-C/n-Si) heterojunctions have been fabricated by direct current magnetron sputtering at room temperature, and their current–voltage characteristics have been investigated. The results show that these junctions have good rectifying properties in the temperature range 80–300 K. The interesting result is that the current–voltage curve changes dramatically with increasing applied voltage and temperature. For the forward bias voltages, the junction shows Ohmic mechanism characteristic in the temperature range 240–300 K. However, the conduction mechanism changes from Ohmic for the low bias voltages to space charge limited current for the high bias voltages in the temperature range 80–240 K. While for the reverse bias voltages, it changes from Schottky emission to breakdown with increasing voltage. Another important phenomenon is that the temperature dependence of the junction resistance shows a metal–insulator transition, whose transition temperature can be controlled by the bias voltage.