Vertical Buffer Leakage and Temperature Effects on the Breakdown Performance of GaN/AlGaN HEMTs on Si Substrate

The epitaxial growth of a GaN/AlGaN HEMTs epi-structure based on a carbon doped superlattice buffer has been optimized for achieving a highly isolated buffer, and transistors with high breakdown voltages and low leakage currents. The 10 mm gate periphery normally-on HEMTs demonstrate a drain-source leakage current lower than 0.4 µA/mm at 600 V drain bias. Furthermore, the breakdown voltage performance of the HEMT is not altered at 600 V bias when the measurement is performed with the substrate being grounded. The isolation blocking voltage of the epi-structure reaches 840 V for a corresponding leakage current density of 10 µA/mm². We highlight low buffer vertical isolation degradation at high temperature (150°C) and that the decrease in HEMT's breakdown voltage performance is not due to the vertical buffer leakage when increasing the substrate temperature.