Estimation of uniformity in Schottky contacts between printed Ni electrode and n-GaN by scanning internal photoemission microscopy

Abstract

We report basic diode characteristics and uniformity of Schottky contacts between printed Ni electrode and n-GaN on GaN epitaxial wafers annealed at 400, 500, and 600 °C. The Schottky barrier height of the samples annealed at 400 °C and 500 °C were as high as 1.21 eV, which is comparable to a conventional evaporated Ni contact. When the annealing temperature was 600 °C, rectifying the characteristics that were lost. Scanning internal photoemission microscopy (SIPM) showed that contacts annealed at 500 °C exhibited better uniformity than those at 400 °C. In contrast, the photo yield signal in SIPM of the contact annealed at 600 °C became weak and noisy due to the interfacial reaction between Ni and GaN. SIPM revealed that the contacts printed Ni electrode on GaN was more uniform than those of the printed Ag electrode. These results also show that SIPM is useful to estimate the uniformity of electrode contacts on semiconductors by non-destructive visualization.