| 摘要 |
PURPOSE:To absorb selectively light of a specified wavelength only, out of input light having many wavelengths, and convert it effectively into photoelectric current, by combining two semiconductor absorption layers whose band gap energy differs with each other. CONSTITUTION:The title semiconductor photodetector comprises a P<+> type InP substrate 1, a P<+> type InP layer 2 and the following formed thereon in order; an N-type InP avalanche region layer 3, a second N-type InGaAs absorption layer 9, an additional electrode 10, and a first N-type InGaAs absorption layer 8. Multi-wavelength light composed of wavelengths lambda1, lambda2 and lambda3 is input to a light receiving surface 5. The energy component of wavelength lambda1 only is totally absorbed, and the respective components of the other wavelengths lambda2 and lambda3 enter the second absorption layer 9 situated in the lower layer. Electron-hole pairs in the first absorption layer 8 which generates as the result of absorbing photon energy are eliminated by the additional electrode 10. In the second absorption layer 9, the energy component of wavelength lambda2 only is converted into photoelectric current, and light having a specified wavelength is output.
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