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

GaN-based metal-insulator-semiconductorinsulator-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 x 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 ZrO2 were 9.79 x 10(-31) A(2)/Hz for f = 10 Hz at 1 V and 335 mu s, respectively, which were lowest compared with the other two samples. ZrO2 was identified as the better GaN, the passivation material among the three dielectrics.