Shockley-Read-Hall lifetime study and implication in HgCdTe Photodiodes for IR detection

Shockley-Read-Hall (SRH) recombination might be a limiting factor of IR photodiodes dark current. This limitation is twofold. SRH generation might occur in the depletion region the photodiode. In that case, the corresponding current is called Generation-Recombination (GR) current, usually limiting low temperature dark current. Moreover, SRH generation might also occur in the diffusion volume, close to the space charge region, resulting in an increase of the diffusion dark current usually limiting the high temperature behavior of the photodiode. Hence, the determination of SRH lifetime of IR materials is of first importance and has to be measured (or at least estimated) to define upcoming trends in future high performance IR detectors. During the last few years, a lot of papers has been published about SRH lifetime in 3-5 materials (InSb, T2SL, InAsSb) and other few communications more focused on comparing different material systems including 3-5s and 2-6 materials. Those latter communications proposes very long SRH lifetime (longer than milliseconds) for HgCdTe, instead of the classical 10 to 100µs usually admitted until now. This paper aims at investigating this SRH lifetime in HgCdTe based on experimental measurements carried out at LETI, on HgCdTe grown in-house. Direct lifetime measurement (photoconductive or photoluminescence decay) as well as indirect estimations from photodiode dark currents will be discussed in order to clarify this question of SRH lifetime and its consequences in upcoming advanced IR detection structures.