Tunneling and 1/ f noise currents in HgCdTe photodiodes

Abstract

The 1/f noise currents and the dc dark current–voltage characteristics are measured over a wide range of reverse bias voltages (0≤Vd≤−1.5 V) and operating temperatures (30–120 K). The diodes are fabricated by ion implanting boron (n+) on bulk p-type material with x≊0.22. Native anodic sulfide in combination with deposited ZnS is used for surface passivation. The dc dark currents of the photodiodes are modeled to extract the tunneling currents from the measured dark currents. The modeling takes into consideration diffusion, generation–recombination, and the two types of tunneling currents (trap assisted tunneling and band to band tunneling). The measurements demonstrate that the dominant mechanism that produces 1/f noise in HgCdTe photodiodes is tunneling, in particular trap assisted tunneling. The correlation between the 1/f noise currents and the dc tunneling currents is given by In=α(It)β(f )−1/2, where It is the tunneling current. The empirical factors β and α are approximately β≊0.5 and α≊1×10−6 for a wide range of temperatures and reverse bias voltages, where the dominant tunneling mechanism is associated with trap assisted tunneling.