Over 600 V Lateral AlN-on-AlN Schottky Barrier Diodes with Ultra-Low Ideality Factor

Abstract: This letter reports the demonstration of lateral AlN Schottky barrier diodes (SBDs) on single-crystal AlN substrates by metalorganic chemical vapor deposition (MOCVD) with an ultra-low ideality factor ({\eta}) of 1.65, a breakdown voltage (BV) of 640 V, and a record high normalized BV by the anode-to-cathode distance (LAC). The homoepitaxially grown AlN epilayers had much lower defect densities and excellent surface morphology, and the AlN ohmic contacts also showed improvements. At forward bias, the devices exhibited ultra-low {\eta} of 1.65 and high Schottky barrier height of 1.94 eV. The device current was dominated by thermionic emission, while most previously reported AlN SBDs suffered from defect-induced current with much higher {\eta} of >4. Additionally, the devices also had excellent rectifying characteristics with ON/OFF ratios on the order of 10^7 to 10^9 and excellent thermal stability from 298 to 573 K. At reverse bias, the devices showed a high BV of 640 V and record-high normalized breakdown voltage (BV/LAC) in lateral AlN SBDs. This work represents a big step towards high-performance ultra-wide bandgap AlN-based high-voltage and high-power devices.