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 (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 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 μs, 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.