Characteristics of GaN Metal-Insulator-Semiconductor-Insulator-Metal Ultraviolet Photodiodes Using Al 2 O 3 , HfO 2 , and ZrO 2 as Insulators

GaN-based metal–insulator–semiconductor–insulator-metal (MISIM) photodiodes using three kinds of high-k dielectrics (Al 2 O 3 , HfO 2 , and ZrO 2 were fabricated, and their electrical, photo response, and noise properties were characterized. The GaN MISIM photodiode using ZrO 2 showed the lowest dark current density of $5.43 \times 10^{-9}$ A/cm 2 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 ZrO 2 were $9.79 \times 10^{-31}~\text{A}^{2}$ /Hz for $f = 10$ Hz at 1 V and $335~\mu \text{s}$ , respectively, which were lowest compared with the other two samples. ZrO 2 was identified as the better GaN, the passivation material among the three dielectrics.