MOCVD Growth and Fabrication of Vertical P-i-N and Schottky Power Diodes Based on Ultra-wide Bandgap AlGaN Epitaxial Structures

We report epitaxial growth of
$\sim$
5-J.1m-thick high-AI-composition (HAC) AlGaN heterostructures on sapphire substrates by metal organic chemical vapor deposition (MOCVD). Cross-sectional and plan view transmission electron microscope (TEM) characterization was carried out to examine the dislocation behavior and density in the thick HAC AlGaN layer. Vertical AlGaN-based P-i-N and Schottky power diodes with state-of-the-art performance are fabricated and characterized, featuring measured breakdown voltages of 1032 V and 685 V, and calculated average breakdown electric fields of 3.44 MV /cm and 2.44 MV/cm, respectively. Both the P-i-N and Schottky diodes exhibit a much higher on/off ratio of
$\sim 10^{8}$
, compared to their ultra-wide bandgap counterparts of AIN based vertical diodes. The AlGaN P-i-N diodes exhibit stable on-state performance under 6–12 V /0.5-1000 s stress test, while a slight shift in the turn-on voltage is observed from the AlGaN-based Schottky diodes under 8 V/0.5-1000 s stress.