Abstract

Graphitic carbon nitride (g-C3N4), a highly stable wide bandgap material, is yet to be evaluated for thin-film applications in devices since its basic electrical properties are not understood. We study its vacuum-deposited thin film form, and in combination with Al2O3, in sandwiched devices using capacitance–voltage (C-V) and current–voltage (I-V) characteristics over a wide range of temperatures and frequencies. The dielectric constant of g-C3N4 alone is between 7 and 8 for frequencies 100 Hz to 100 kHz, but it is almost double at 14–16 when used in conjunction with a thin layer of Al2O3. The increased dielectric constant is attributed to additional polarization at the interface of the two dielectrics. The leakage current density is of the order of 10–7 A/cm2 and shows slight asymmetry. The mechanisms of current transport are mainly space charge limited at fields higher than 5 × 105 V/cm. We attribute the small but significant difference between forward and reverse bias to the presence of the negative sheet charge at the interface between the two dielectrics. The interfacial charge density is estimated to be 1011 cm−2.