Dark current and 1/f noise characteristics of In0.74Ga0.26As photodiode passivated by SiNx/Al2O3 bilayer

This study is focusing on dark current and 1/f noise characteristics of In0.74Ga0.26As photodiode passivated with different passivation films. With regard to mesa-type wavelength-extended InGaAs photodiode, surface passivation process plays an important role in reducing the excess leakage current of the device. With the development of passivation process, atomic layer deposition (ALD) has been used in the fabrication process of photodetectors. In order to reduce the side current of In0.74Ga0.26As photodiodes, SiNx film and SiNx/Al2O3 bilayer have been considered as the passivation film, respectively. The dark current test results indicate that SiNx/Al2O3 bilayer can effectively reduce side current of In0.74Ga0.26As photodiodes compared to SiNx film. Moreover, the results of noise frequency spectra qualitatively demonstrate that SiNx/Al2O3 bilayer can significantly decrease the interface states density, thereby reducing the 1/f noise of photodiodes.