| 摘要 |
PROBLEM TO BE SOLVED: To provide a wavelength sensor whose degree of the absorption of light with long wavelength differs and which can identify wavelength from the ratio of optical current, by selectively forming a silicon germanium layer whose light absorption coefficient is larger than silicon by not less than 20 times in a part of a silicon photodiode without using dye whose color easily fades. SOLUTION: In a wavelength sensor, silicon germanium layers 4 different in thickness are deposited on plural first conductive silicon layers 1 separated by an insulating film. Second conductive impurity is diffused on the silicon germanium layers 4 and the light of long wavelength is absorbed by the silicon germanium layers 4. Thus, photodiodes 16 can obtain different optical currents with respect to the wavelength of light.
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