Fabrication and device characteristics of bulk GaN-based Schottky diodes

In this investigation, Schottky diodes with different device sizes (150 mu m, 420 mu m and 700 mu m) were fabricated on the Ga-face of a free-standing n-GaN wafer produced by Kyma Technologies, Inc. Full area back side ohmic contact was prepared on the 4-face of the bulk GaN using Ti/Al. Without any edge-termination scheme, a relatively high reverse breakdown voltage of 240V was achieved. The reverse breakdown voltage decreases as the device size increases'. The forward turn-on voltage was as low as 2.4V at room temperature for the 150 mu m diameter Schottky diodes. The best on-state resistance was 7.56 m Omega cm(2) for diodes with V-B=240V, producing a figure-of-merit (V-B(2)/R-ON) of 7.6 MWcm(-2). The Schottky diode also showed an extremely short reverse recovery time (< 20 ns) switching from forward bias to reverse bias.