The present invention is based on the finding of the inventors that at the lattice mismatching degree Δa/a between the GaInAs light absorbing layer and the InP buffer layer in the positive range {HEAD ~ the dark current} is lower than {TAIL ~ the negative range} at room temperature 
is lower than
The present invention is based on the finding of the inventors that at the lattice mismatching degree Δa / a between the GaInAs light absorbing layer and the InP buffer layer in the positive range { HEAD ~ the dark current } is lower than { TAIL ~ the negative range } at room temperature
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