High-voltage high-current vertical geometry Ga₂O₃ rectifiers

There are continuing rapid developments in vertical geometry Ga₂O₃ for high voltage switching applications. Ga₂O₃ is emerging as a viable candidate for certain classes of power electronics with capabilities beyond existing technologies due to its large bandgap, controllable doping and the availability of large diameter, relatively inexpensive substrates. These include power conditioning systems, including pulsed power for avionics and electric ships, solid-state drivers for heavy electric motors and advanced power management and control electronics. There are already cases where the performance exceeds the theoretical values for SiC. Existing Si, SiC (vertical devices), and heteroepitaxial GaN (lateral devices) enjoy tremendous advantages in terms of process maturity, an advantage that is especially true for Si, where the ability to precisely process the material has resulted in devices such as super-junctions that surpass the unipolar "limit". Continued development of low defect substrates, optimized epi growth and surface treatments and improved device design and processing methods for Ga₂O₃ are still required to push the experimental results closer to their theoretical values. Even 3 μm epi layers with doping concentration of 1016 cm-3 should have a theoretical breakdown voltage of ∼1800V. The actual experimental value of VB is currently well below the theoretical predictions. Thermal management is a key issue in Ga₂O₃ power devices for practical high current devices and initial studies have appeared on both the experimental and theoretical fronts. We summarize progress in edge termination design, temperature measurement using thermoreflectance-based thermography to measure the thermal rise and decay of the active diodes, failure under forward bias and development of large current (up to 130A) arrays.