Finite Element Method Modeling of Optoconductance in Metal-Semiconductor Hybrid Devices

Girgis, Alexi M

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Finite Element Method Modeling of Optoconductance in Metal-Semiconductor Hybrid Devices

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A numerical description of the extraordinary optoconductance (EOC) effect is presented using two separate models. Extraordinary optoconductance is part of a general class of EXX geometric effects involving the external perturbation of the properties of a 2D electron gas in a macroscopic semiconductor or metal-semiconductor hybrid structure. The addition of metallic inclusions, has been shown to increase the sensitivity of devices relying on EXX effects. Following the discovery of the first EXX effect, extraordinary magneto-resistance (EMR), an optical equivalent was suggested. Unlike EMR, where the external perturbation is an applied magnetic field, EOC results from the modification of the local charge density in the semiconductor by a focused laser. The first model assumes Gaussian charge densities for the photo-generated electron-hole pairs while the second model directly solves the semiconductor drift-diffusion equations using the finite element method (FEM). Results from both models are shown to agree with experimental EOC data, both as a function of the laser spot position and temperature. The FEM model has the ability to describe EOC in more complex geometries making it useful in designing EOC devices geared for particular applications.

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