Characteristics of GaN Metal-Insulator-Semiconductor-Insulator-Metal Ultraviolet Photodiodes Using Al₂O₃, HfO₂, and ZrO₂ as Insulators

GaN-based metal-insulator-semiconductor-insulator-metal (MISIM) photodiodes using three kinds of high-k dielectrics (Al₂O₃, HfO₂, and ZrO₂ were fabricated, and their electrical, photo response, and noise properties were characterized. The GaN MISIM photodiode using ZrO₂ showed the lowest dark current density of 5.43 × 10-9 A/cm² at 10 V bias and the highest UV-visible rejection ratio of 257 at 1 V bias. No Fowler-Nordheim tunneling phenomenon was observed in the diode under UV illumination. The noise spectral density and the trap-time-constant of the device using ZrO₂ were 9.79 × 10-31A2 /Hz for f = 10 Hz at 1 V and 335μs, respectively, which were lowest compared with the other two samples. ZrO₂ was identified as the better GaN, the passivation material among the three dielectrics.