Analysis of bulk and surface components of leakage current in 4H-SiC PiN MESA diodes

The leakage current in circular- and ring-shaped epitaxial 4H-SiC PiN mesa diodes with different size and periphery to area ratios was evaluated under the influence of the UV irradiation and temperature in the range from room temperature (RT) to 250 °C. The surface leakage current component was found to dominate the reverse current characteristics and was found to be dependent on time and temperature both after reactive ion etching (RIE) of the diodes in the SF6/Ar gas mixture and after the UV irradiation. Charging of the surface states is believed to be responsible for the observed behavior. The UV irradiation is believed to charge the surface positively. The drift of the I(V) characteristics is due to the trapping of the electrons neutralizing the positive donor states.