Ultrawide Bandgap Diamond/ε-Ga₂O₃ Heterojunction pn Diodes with Breakdown Voltages over 3 kV

Robust bipolar devices based on exclusively ultrawide bandgap (UWBG) semiconductors are highly desired for advanced power electronics. The heterojunction strategy has been a prevailing method for fabricating a bipolar device due to the lack of effective bipolar doping in the same UWBG material. Here, we demonstrate a unique heterojunction design integrating the p-type diamond and n-type ε-Ga₂O₃ that achieves remarkable breakdown voltages surpassing 3000 V. Despite the lattice mismatch, the heteroepitaxial ε-Ga₂O₃ film is established on the diamond substrate, forming an atomically sharp interface with C-O-Ga bonding and enabling the O-terminated diamond surface for constructing an effective rectifying heterojunction. The ultra-high-quality interface, together with the lightly doped diamond as the drift layer, largely weakens the commonly met electric field crowding effect in power diodes and provides a cost-effective thermal management route. This study provides an efficient heterojunction design to realize the potential of UWBG semiconductors for ultra-high-power applications.