A model for dark current and multiplication in HgCdTe avalanche photodiodes |
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Authors: | S Velicu R Ashokan S Sivananthan |
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Affiliation: | (1) Department of Physics, University of Illinois at Chicago, Microphysics Laboratory, 60607 Chicago, IL |
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Abstract: | In this paper we report the calculated results of the dark current and multiplication factor in MBE grown HgCdTe avalanche
photodiodes with separate absorption and multiplication (SAM-APD). The device architecture used for this analysis comprises
the following layers: p+ contact, p junction, n− multiplication, n charge sheet, n− absorber, and n+ contact. Various leakage current mechanisms are considered and the generation-recombination term is found to be the dominant
one for this device structure. However, experimental reverse bias I-V characteristics reported earlier by T. de Lyon et al.
shows a large deviation from ideality, which can not be explained in terms of bulk leakage current mechanism. To explain the
large difference between experimental and theoretical data we consider that the dominant generation-recombination current
is multiplied through impact ionization process. To validate this assumption, multiplication is calculated as a function of
reverse bias. Electric field profile is obtained and the multiplication is computed using the ionization coefficients and
avalanche gain equations. Breakdown voltage is found to be 85 V for room temperature operation in agreement with available
data in the literature. The theoretical I-V curves considering multiplication are compared with the experimental ones and
a close agreement is found which validate this model. |
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Keywords: | Avalanche photodiode HgCdTe MBE dark current multiplication |
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