Estimates of Impact Ionization Coefficients in Superlattice-Based Mid-Wavelength Infrared Avalanche Photodiodes
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Estimates of Impact Ionization Coefficients in Superlattice-Based Mid-Wavelength Infrared Avalanche Photodiodes C.H. Grein1, K. Abu El-Rub1,2, M.E. Flatté3, and H. Ehrenreich4 Microphysics Laboratory and Department of Physics, University of Illinois at Chicago, Chicago, IL 60607-7059 2 Department of Physics, Jordan University of Science & Technology, Irbid-Jordan 3 Optical Science and Technology Center and Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 4 Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 1
ABSTRACT We describe band engineering strategies to either enhance or suppress electron-initiated impact ionization relative to hole-initiated impact ionization in type II superlattice midwavelength infrared avalanche photodiodes. The strategy to enhance electron-initiated impact ionization involves placing a high density of states at approximately one energy gap above the bottom of the conduction band and simultaneously removing valence band states from the vicinity of one energy gap below the top of the valence band. This gives the electrons a low threshold energy and the holes a high one. The opposite strategy enhances hole-initiated impact ionization. Estimates of the electron (α) and hole (β) impact ionization coefficients predict that α/β>>1 in the first type of superlattice and α/β
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