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

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