Reverse Breakdown in Large Area, Field-Plated, Vertical β-Ga2O3 Rectifiers

Abstract

There is interest in developing large area Ga2O3 rectifiers for applications in hybrid power converters. Vertical geometry, Schottky rectifiers with area 1.2 × 1.2 mm2 fabricated on thick (8μm), undoped (n = 4.4 × 1015 cm−3) β-Ga2O3 epitaxial layers oN conducting bulk substrates exhibit both high forward current (1A in pulsed mode) and reverse breakdown voltage (VB = 760V). This breakdown voltage was ∼200V higher than rectifiers without the presence of a bilayer SiO2/ SiNx field plate. This edge termination is critical for obtaining high breakdown voltage by reducing electric field crowding around the metal contact periphery. Optimization of the field plate design is still needed, since devices are observed experimentally to breakdown at the contact periphery. When purposely driven to failure at high reverse bias, pits are observed in the high field regions at the edge of the contact. The specific on-resistance (Ron) for these large area rectifiers was 22 mΩ.cm−2, with a figure-of-merit VB2/Ron of 26 MW.cm−2. The potential of Ga2O3 for power electronics is clear when it is realized that these values are still an order of magnitude lower than theoretical values. The diode on-off ratio was in the range 2.7 × 107–2.2 × 109 when switching from +1.5V forward bias to 1–100V reverse bias.