| 摘要 |
PURPOSE:To detect light of shorter wavelength than that of a main wavelength band to be detected by selectively disposing a cap layer having a larger forbidden band width than a light absorption layer on the front face of the layer. CONSTITUTION:A cap layer 4 having a larger forbidden band width than that of light absorption layer 3 is selectively disposed on the front face of the layer 3 which can photodetect and obtain the longest wavelength of the band to be detected. In this case, the degree of freedoms for controlling the forbidden band width of the layer 4, i.e., the composition, the area ratio to the total photodetecting area, pattern shape, the thickness selection and, as required, the quantum efficiency of short wavelength side, such as the weight of the cap layer having different a plurality of compositions is large to obtain a semiconductor photodetector adapted to intended purposes with characteristics of dark current. Thus, it can detect a short wavelength light and cope with composite photodetecting function required for an optical application system.
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