Analysis of dark current and 1/f noise in long-wavelength infrared $Hg_{1-x}Cd_xTe$ photodiodes

Abstract

In this thesis, two subjects have been studied. One is about the analysis of the I-V characteristics in LWIR HgCdTe photodiodes using dark current modeling and fitting procedure. The other is the study on finding the relationship between excess low frequency (1/f) noise currents and dark currents for various bias voltages and variable-area diode array structure. Dark current models in HgCdTe photodiodes are summarized. The dark currents are composed of diffusion current, generation-recombination (g-r) current, band-to-band tunneling (BTB) current and trap-assisted tunneling (TAT) current. Using these models, we investigated the post-implantation annealing effects on LWIR HgCdTe photodiodes. Devices were fabricated by ion-implantation technique and their characteristics, such as current-voltage and dynamic resistance-voltage, were examined. Current-voltage and resistance-voltage characteristics were investigated after the post-implantation annealing at 150℃. During the fitting analysis, different four dark currents could be successfully separated and the improvement in the diode performances, brought about by the annealing process, could be well explained. The characteristics of 1/f noise of HgCdTe diodes have been studied. First, the measurement of the 1/f noise was carried out for the diodes in chapter 2, and it was found, from the model fitting analysis, that the 1/f noise current is strongly correlated with the trap density. As the annealing time increased, both the 1/f noise current and the trap density changed in a similar manner. Even though RdA-V characteristics for 30 min. and 1 hour annealed diodes looked similar, the diode annealed for 1 hour showed lower 1/f noise current than that for 30 minutes. It is probably due to lower trap density of the diode annealed for 1 hour, in other words, due to smaller trap-assisted tunneling current component comparing with that for 30 minutes. Second, the relationship between 1/f noise and dark current in LWIR HgCdT...