Spectral reflectance and responsivity of Ge- and InGaAs-photodiodes in the near-infrared: measurement and model
The spectral reflectance and responsivity of Ge- and InGaAs-photodiodes at (nearly) normal and oblique incidence (45 degree sign ) were investigated. The derived data allow a calculation of the photodiodes responsivities for any incident angle. The measurements were carried out with s-and p-polarized radiation in the wavelength range from 1260 to1640 nm. The spectral reflectance of the photodiodes was modeled by using the matrix approach developed for thin-film optical assemblies. The comparison between the calculated and measured reflectance shows a difference of less than 2% for the Ge-photodiode. For the InGaAs-photodiode, the differences between measured and calculated reflectance are larger, i.e., up to 6% for wavelengths between 1380 and1580 nm. Despite the larger differences between calculated and measured spectral reflectances for the InGaAs-photodiode, the difference between calculated and measured spectral responsivity is even smaller for the InGaAs-photodiode than for the Ge-photodiode, i.e.,?1.2% for the InGaAs-photodiode compared to?2.2% for the Ge-photodiode. This is because the difference in responsivity is strongly correlated to the absolute spectral reflectance level, which is much lower for the InGaAs-photodiode. This observation also shows the importance of having small reflectances, i.e.,appropriate antireflection coatings for the photodiodes. The relative standard uncertainty associated with the modeled spectral responsivity is about 2.2% for the Ge-photodiode and about 1.2% for the InGaAs-photodiode for any incident angle over the whole spectral range measured. The data obtained for the photodiodes allow the calculation of the spectral responsivity of Ge- and InGaAs-trap detectors and the comparison with experimental results.
- OSTI ID:
- 21013688
- Journal Information:
- Applied Optics, Vol. 46, Issue 29; Other Information: DOI: 10.1364/AO.46.007337; (c) 2007 Optical Society of America; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6935
- Country of Publication:
- United States
- Language:
- English
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