III-V Heterostructure Avalanche Photodiode Modules for Fiber Optic Communication Links in the 1.0 to 1.3 Micrometer Spectral Range.

InGaAsP APDs have been fabricated with uniform high-speed gains up to 42 and quantum efficiencies up to 70 at 1.28 micrometers. At high gains increased leakage current leads to excessive shot noise and gain saturation. Noise measurements indicate that the increased leakage current arises from a uniformly multiplied but increasing value of the primary i.e., premultiplication leakage current. To try to reduce this leakage current, various procedures for fabricating guard ring APDs have been studied. Preliminary guard ring structures have demonstrated guard ring isolation by exhibiting avalanche gain in the central region only. However, these initial guard ring APDs need further development before a meaningful comparison can be made to APDs without guard rings. Author