High breakdown voltage Schottky rectifier fabricated on bulk n-GaN substrate

Abstract

Vertical Schottky rectifiers have been fabricated on a free-standing n-GaN substrate. Circular Pt Schottky contacts with different diameters (50μm, 150μm and 300μm) were prepared on the Ga-face and full backside ohmic contact was prepared on the N-face by using Ti/Al. The electron concentration of the substrate was as low as ∼7×1015cm−3. Without epitaxial layer and edge termination scheme, the reverse breakdown voltages (VB) as high as 630V and 600V were achieved for 50μm and 150μm diameter rectifiers, respectively. For larger diameter (300μm) rectifiers, VB dropped to 260V. The forward turn-on voltage (VF) for the 50μm diameter rectifiers was 1.2V at the current density of 100A/cm2, and the on-state resistance (Ron) was 2.2mΩcm2, producing a figure-of-merit (VB)2/Ron of 180MWcm−2. At 10V bias, forward currents of 0.5A and 0.8A were obtained for 150μm and 300μm diameter rectifiers, respectively. The devices exhibited an ultrafast reverse recovery characteristics, with the reverse recovery time shorter than 20ns.