Vertical Leakage and Back-Gating Characteristics of GaN HEMTs Based on GaN/AlN Epitaxy on Off-Axis Conducting 4H-SiC

As wide-bandgap semiconductors, GaN and SiC have been regarded as silicon's successors in a wide range of power electronic applications and developed independently for decades. The mainstream GaN and SiC-based power devices exhibit complementary merits and drawbacks, which sparks the effort to integrate them on a single platform. This work studies a feasible configuration in GaN/SiC integration, with GaN-based heterojunction epi-structure to be grown on off-axis and conducting 4H-SiC substrates. The vertical leakage and back-gating characteristics of GaN high-electron-mobility transistors (HEMTs) made on GaN/AlN epitaxy on off-axis 4H-SiC substrates with different surface doping are investigated. It is revealed that the conducting SiC substrates can inject both electrons and holes into the GaN/AlN epi-layer above. The presence of the AlN transition layer on SiC is speculated as the major cause for such phenomena as its constituent elements, Al and N, can act as acceptor and donor in SiC, respectively.