The Origins of Leaky Characteristics of Schottky Diodes on p-GaN

Abstract—The possible origins of leaky characteristics of Schottky barrier on p-GaN have been investigated. The as-grown samples did not show any electrical activities using Hall measure-ments. Ni diodes made on as-activated samples, either at 950 C for 5 s or at 750 C for 5 min exhibited quasiohmic behavior. Upon sequential etching of the sample to remove a surface layer of 150 Å, 1200 Å, and 5000 Å from the sample, the – behavior became rectifying. – – measurements showed that the slopes of the ln – curves were independent of the temperature, indicative of a prominent component of carrier tunneling across the Schottky junction. – measurements at each etch-depth indicated a decreasing acceptor concentration from the surface. The highly doped ( 1.7 1019 cm 3) and defective surface region (within the top 150 Å from surface) rendered the as-activated Schottky diodes quasiohmic in their – characteristics. The leaky – characteristics, often reported in the literature, was likely to be originated from the surface layer, which gives rise to carrier tunneling across the Schottky barrier. This highly doped/defective surface region, however, can play an important role in ohmic contact formation on p-GaN