Dark current reduction of avalanche photodiode using asymmetric InGaAsP/InAlAs superlattice structure

We studied dark current reduction of avalanche photodiode using asymmetric InGaAsP/InAlAs superlattice structure, which were fabricated by gas-source molecular beam epitaxy. Band-to-band tunneling current, which dominates dark current property, was suppressed by increasing effective band gap energy of asymmetric superlattice multiplication layer. The dark current for sample C, which has the thickest barrier and the thinnest well thickness in samples, is the lowest among samples at any multiplication factor. In sample C, the dark current value at a M = 10 was 0.4 mu A. This is the smallest value of dark current for InGaAsP/InAlAs SL-APD, as we know. It is found that adopting asymmetric superlattice structure decreases the electric field for multiplication layer and it also improve dark current property.