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

Abstract

The long-wavelength infrared Hg1-xCdxTe photovoltaic dete ctors 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 meas urements 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 mechan isms indicated that the performance of the diode passivated by single ZnS was st rongly affected by tunneling current related to the surface defects, which was r esponsible for the dark currents and 1/f noise characteristics. By the analy sis of x-ray reciprocal space map (RSM), it was found that the Qy dir e ction broadening of HgCdTe epitaxial layer passivated by ZnS was wider after pas sivation, which confirmed the existence of defects in the surface of HgCdTe epit axial layer passivated by ZnS. In order to investigate the effect of surface pas sivation on the stability of two kinds of diodes, dark currents and 1/f nois e of the diodes were measured after vacuum baking for 10 h at 80℃. The dark cur rent 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 wa s found that the Qy direction broadening of HgCdTe epitaxial layer pa s sivated 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.