| 摘要 |
PROBLEM TO BE SOLVED: To prevent the stray light of transmission light from entering by providing an absorption layer for selectively absorbing the transmission light on a substrate and at the same time directly below a light receiving layer in a device for transmitting and receiving reception light with long wavelength and the transmission light with short one. SOLUTION: Incidence light A ofλ2 entering from backside is absorbed by a depletion layer 62 for forming an electron/hole pair. This is a region for picking up light. By backward biasing, the electron and hole run to n- and p-type regions, respectively, for allowing photocurrent to flow. This is photoelectric conversion operation of normal PD. However, incidence light B ofλ1 (transmission light wavelength) similarly entering from the backside is absorbed by an n+-InGaAsP absorption layer 58. Since the light B ofλ1 does not reach a light receiving layer 59, the PD does not have sensitivity to the transmission light wavelengthλ1. Even when incidence light C of theλ1 enters the PD from a slanting lower part, the incidence light C is absorbed by the absorption layer 58 and does not reach the light receiving layer 59, thus preventing sensitivity to light B and C ofλ1.
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