Patent ID: 7274081

Claim:
A front-illuminated-type photodiode array comprising: (a) a first-electroconductive-type semiconductor substrate; (b) a first-electroconductive-type electrode placed at the rear-face side of the semiconductor substrate; (c) a first-electroconductive-type absorption layer that: (c1) is formed at the front-face side of the semiconductor substrate; and (c2) has an absorption edge wavelength of λ gr ; (d) a plurality of lightwave receiving parts comprising: (d1) a plurality of second-electroconductive-type regions formed from the surface of the absorption layer to a certain distance into the absorption layer such that the regions are arranged one- or two-dimensionally; and (d2) a second-electroconductive-type electrode provided at a part of each of the second-electroconductive-type regions; (e) an antireflective coating that: (e1) covers the top surface other than the individual second-electroconductive-type electrodes; and (e2) is for preventing the reflection of an incoming lightwave; (f) at least one first-electroconductive-type leakage-lightwave-absorbing layer that: (f1) is provided between the first-electroconductive-type electrode and the absorption layer; and (f2) has an absorption edge wavelength, λ ga , equal to or longer than the absorption edge wavelength, λ gr , of the absorption layer (λ gaγ ≧λ gr ); and (g) a first-electroconductive-type buffer layer that: (g1) is provided between the absorption layer and the at least one leakage-lightwave-absorbing layer; and (g2) has an absorption edge wavelength, λ gb , shorter than the absorption edge wavelength, λ gr , of the absorption layer (λ gb <λ gr ).