Hg/sub 0.4/Cd/sub 0.6/Te 1.55- mu m avalanche photodiode noise analysis in the vicinity of resonant impact ionization connected with the spin-orbit split-off band

The authors describe the electrical and optical characterization of three Hg/sub 1-x/Cd/sub x/Te avalanche photodiodes manufactured using planar technology with composition parameter x near 0.6. This alloy composition leads to devices that are well suited for 1.55- mu m detection. From the noise analysis under multiplication, the authors show the tight dependence of the ratio beta / alpha (of the hole; and electron ionization coefficient, respectively) upon x and the ratio Delta /E/sub g/ where Delta is the spin-orbit splitting energy and E/sub g/ is the bandgap energy. It turns out that in these alloys around x=0.6, Delta is very close to the bandgap energy so beta / alpha reaches its maximum value. Owing to this property, which is characteristic of II-VI compounds, Hg/sub 1-x/Cd/sub x/Te is a good candidate for 1.3- mu m to 1.6- mu m avalanche photodiodes.<
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