Semiconductor radiation wavelength detector

Details Semiconductor radiation wavelength detector Semiconductor radiation wavelength detector

1975-09-23

1977-03-08

Smith, Alfred E.

Optics: measuring and testing

Refraction testing

Prism engaging specimen

250211J, 357 30, G01J 346, H01J 3912, H01L 2714

Patent

active

040110168

ABSTRACT:
A double-layer photodiode is created in an integral structure to form two diodes, the upper diode having a relatively thin active region and the lower diode a relatively thick active region. Light whose wavelength is to be measured is directed onto the upper diode. The thickness of the first diode is chosen so that, in the spectrum of light wavelengths being measured, the energy of the shortest wavelength is entirely absorbed therein. As the radiation wavelength increases, the absorption by the upper diode decreases exponentially, and the unabsorbed light is transmitted through the thin active region into the thick active region of the lower diode where it is absorbed. The thickness of the active region of the lower diode is chosen so that it absorbs substantially all of the energy of longest wavelength in the spectrum being measured. The absorption of the photon energy in each diode creates electron-hole pairs therein which produce in each diode a change in conductivity which is proportional to the absorbed energy. Therefore, since the difference in conductivities of the two diodes is a function of the wavelength of the incident light, as the wavelength changes, the difference between changes in the conductivity of the two diodes, divided by the sum of the changes in conductivity, is a function which is a single-valued function of the wavelength of the incident light and which is independent of the intensity of the incident light. A measuring circuit connected to the double-layer diode provides a direct reading of the wavelength. Furthermore, there is disclosed a method for fabricating a double-layer photodiode suitable for use in the wavelength detector.

REFERENCES:
patent: 3304430 (1967-02-01), Biard et al.
patent: 3478214 (1969-11-01), Dillman
patent: 3484663 (1969-12-01), Halus

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