Analysis of surface leakage and 1/f noise on long-wavelength infrared HgCdTe photodiodes

The long-wavelength infrared Hg1-x Cd-x Te photovoltaic detectors with x = 0.217 passivated by single ZnS layer and dual (CdTe + ZnS) layers were fabricated in the same wafer. The fabricated devices were characterized by measurements of dark currents and 1/f noise. The diode passivated by dual (CdTe + ZnS) layers showed a higher performance compared to the diode passivated by the single ZnS layer at high reverse bias, and modeling of diode dark current mechanisms indicated that the performance of the diode passivated by single ZnS was strongly affected by tunneling current related to the surface defects, which was responsible for the dark currents and 1/f noise characteristics. By the analysis of x-ray reciprocal space map (RSM), it was found that the Q(y) direction broadening of HgCdTe epitaxial layer passivated by ZnS was wider after passivation, which confirmed the existence of defects in the surface of HgCdTe epitaxial layer passivated by ZnS. In order to investigate the effect of surface passivation on the stability of two kinds of diodes, dark currents and 1/f noise of the diodes were measured after vacuum baking for 10 h at 80 degrees C. The dark current mechanisms indicated that the performance of the diode passivated by single ZnS was strongly affected by the surface defects. By the analysis of RSM, It was found that the Q(y) direction broadening of HgCdTe epitaxial layer passivated by ZnS was wider after high-temperature baking, which also confirmed the existence of defects in the surface of HgCdTe epitaxial layer passivated by ZnS after baking.