Properties of Ion-Implanted and Diffused Photodetectors of Germanium and Germanium-Silicon Alloys
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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The response of planar shallow-junction Ge photodiodes displayed peak performance at the expected 1.46 micrometers wavelength. Responsivity and quantum efficiency were measured at approximately 0.9 micro Amicro W and approximately 80, respectively, with leakage currents of approximately 6 micro A, typical for Ge photodiodes. Leakage currents were notably decreased in diffused diodes. The high values for responsivity and quantum efficiency could be attributed to the shallow junction approximately 1 micrometer designed to increase the amount of photogenerated current which could be collected by the p- n junction. The reason for the interest in photodetectors lies in fiber-optic applications. Minimum fiber attenuation and dispersion occurs near 1.27 micrometers. Photodetectors at this wavelength require tailoring of the bandgap energy of Ge by adding about 10 Si. A quantum mechanical analysis of the energy band structure of the Ge-Si alloy is included with suggestions to obtain energy gap and effective mass values experimentally. Ge-Si photodetectors fabricated as shallow-junction photodiodes should exhibit high photoresponse and quantum efficiency near 1.27 micrometers.
- Physical Chemistry
- Metallurgy and Metallography