Dark current and noise analysis for Long-wavelength infrared HgCdTe avalanche photodiodes

Abstract

In this paper, the temperature-dependent current–voltage (I-V) characteristics (30∼100 K) of planar (n+/n-/p) long-wavelength infrared (LWIR, cutoff-wavelength λc = 11.5 μm at 80 K) HgCdTe avalanche photodiodes (APDs) device were measured and numerical simulated. The parameters in the Okuto-Crowell model were obtained as a function of bandgap and operation temperature, and the results showed that our theoretical model fit well with the experiment. Considering the difficulty of evaluating excess noise factor F at high gains due to the rapid increase in band-to-band tunneling (BBT) current, the effects of BBT on the F measurements were discussed, by means of noise power spectral density (PSD) and noise figure meter. We obtained a low F = 1–1.27@gain (M) = 6 at −2 V and extended the F to a higher gain (M = 23 at −3 V). The bias-dependent dark noise was further studied, and we supposed that the BBT component might partially undergo avalanche multiplication in our LWIR devices. Therefore, suppressing the BBT current by an appropriate annealing process was one possibility to reduce dark current and noise in devices. The method in this paper can provide a reference for performance evaluation in HgCdTe APDs, as well as guidance for designing or optimizing the structure.