WORKSHOP PAPER
Dislocation-free Ge/Si coupling at LCM of their lattice constants, replacing InGaAs/InP
Abstract
Currently, image sensors are used for SWIR imaging. The lattice constants of InGaAs and InP can be matched at 0.5869 nm by adjusting the ratio of In and Ga in InGaAs at 53 vs. 47. Ge and Si are much common materials than InGaAs and InP. However, Ge-on-Si image sensors generate much higher dark current than InGaAs/InP ones. The reason is the mismatch of the lattice constants of Ge, 0.5658 nm, and Si, 0.5431 nm, with a 4.18% difference, causing dislocations at the Ge boundary layer over the Si layer. The dislocations, especially threading diagonally dislocations which penetrate the Ge layer, generate huge dark current. This note provides a simple, yet, perfect solution to solve the problem. The concept is “A polka-dot coupling at pseudo LCM (least common multiple) of the lattice constants of Ge and Si crystals”, in which the Ge and Si layers are connected through an array of openings of an insulation layer separating the Ge and Si layers with the pitch of a sort of LCM of the lattice constants of the Ge and Si crystals.Keywords
Ge, image sensor, dislocation free, LCM Polka-dot coupling,References
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