| 摘要 |
An avalanche photodiode is provided which consists of a staircase APD with a periodic multilayer structure graded in composition from InAlAs to InGaxAl(1-x)As (x>0.1) as the multiplication layer to improve the dark current characteristic. Another photodiode with separate photoabsorption and multiplication regions is provided with an electric-field relaxation layer whose bandgap is wider than that of the photoabsorption and has a triple structure with a highly-doped layer sandwiched between lightly-doped layers. This photodiode incorporates in detail on an n-type InP substrate, an avalanche multiplication layer 13 of a periodic multilayer structure graded in composition from n--InAlAs to InGaxAl(1-x)As, a p--InGaAs photoabsorption layer 17, and an InP electric-field relaxation triple layer 16 consisting of n-, p+, and p- layers between the avalanche multiplication layer 13 and the photoabsorption layer 17.
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