Effects of different passivation layers on RV characteristics of long-wave HgCdTe gate-controlled diodes

This work investigated the effects of different surface passivation layers on the electrical properties of long-wave HgCdTe photodiodes. For better comparison, three types of surface passivation methods, ZnS passivation, CdTe passivation and ZnS/CdTe double passivation, were fabricated in one chip to produce gated diodes. Passivation film is the only difference between these devices. The experimental results show that under the gate voltage control, the diodes formed by the three passivation methods will experience the accumulation, flat band, depletion and inversion states below the gate structure. At the same time, the R-V characteristic curves of their dark currents can be well fitted to the existing model to obtain the diffusion current, the generation-recombination current, the trap assisted tunneling current, and the band-to-band tunneling current. However, different passivation layers have different gate voltage ranges corresponding to the same process. By fitting the body parameters obtained from the RV curve under the flat band voltage, it can know that different surface passivation does not affect the device body parameters, and the surface bias formed by CdTe/ZnS double passivation has the most significant effect on the device. The ZnS and CdTe/ZnS double passivation films have similar insulating properties and are superior to CdTe passivation films.