Metal/BaTiO 3 / $\beta$ -Ga 2 O 3 Dielectric Heterojunction Diode with 5.6 MV/cm Breakdown Field

$\beta$ -Ga203 is an emerging ultra-wide bandgap (~4.7 eV) semiconductor with great potential for power electronics. The large breakdown electric field (6–8 MV/cm predicted) due to wide band gap combining with electron mobility of 250 −300 cm2/Vs offers a higher figure of merit for power electronic than SiC and GaN. In the absence of a p-type dopant, the low Schottky barrier height is a fundamental challenge for achieving the theoretically predicted limit for $\beta$ -Ga 2 O 3 power electronic devices. $\beta$ -Ga 2 O 3 Schottky barrier diodes with more than 1 kV breakdown voltage have been demonstrated but the maximum breakdown field in these devices was limited below 3.5 MV/cm due to metal to Ga203 Schottky barrier height (1.5-1.7 eV). In this work, we design and demonstrate the use of high dielectric heterojunctions to engineer electrostatics and transport within the diode and achieve high breakdown electric field (5.6 MV/cm) in a metal/BaTiO 3 $\beta$ -Ga 2 O 3 heterojunction diode. This is the highest reported breakdown field for any $\beta$ -Ga 2 O 3 vertical diode, and it provides a general framework for future design of unipolar high voltage diodes based on wide and ultra-wide bandgap semiconductors.