14 August 2003 High-speed heterostructure avalanche photodiodes
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It has been shown recently that the noise and speed characteristics of avalanche photodiodes (APDs) can greatly benefit from the presence of a reasonable amount of initial energy stored in the injected carriers that initiate the avalanche process. The benefits range from reduced excess noise factor, increased abruptness in the breakdown probability, as well as an increase in the bandwidth. The key mechanism for the improved performance is the significant reduction of the first dead space in the ionization process. The dead space is the minimum distance a carrier must travel before acquiring sufficient kinetic energy enabling it to impact ionize. The reduction of the first dead space has the effect of localizing the first impact ionization and forcing it to occur quickly near the edge of the multiplication region. This, in turn, will have the effect of nearly inducing two avalanche processes that run in parallel and whose combination will yield the total gain. In this talk, a theoretical model for the avalanche multiplication is utilized to examine the fundamental limits of the gain-bandwidth product in light of the initial-energy effect in practical APD structures.
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Majeed M. Hayat, Majeed M. Hayat, Oh-Hyun Kwon, Oh-Hyun Kwon, "High-speed heterostructure avalanche photodiodes", Proc. SPIE 5246, Active and Passive Optical Components for WDM Communications III, (14 August 2003); doi: 10.1117/12.511218; https://doi.org/10.1117/12.511218

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