Investigation of nonlinear oscillations in the gas discharge-semiconductor system: Effect of different fluid modelling approaches

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Edebiyat Fakültesi, Fizik Bölümü, Türkiye

Tezin Onay Tarihi: 2018

Öğrenci: CİHAN YEŞİL

Danışman: İSMAİL RAFATOV

Özet:

The work deals with the study of nonlinear oscillations in a system, consisted of planar glow discharge layer, coupled to a high-ohmic semiconductor layer. The whole system is sandwiched between two planar electrodes, to which the DC voltage is applied. The discharge models are developed in Comsol Multiphysics (v5.2), and based on fluid description of plasma, with drift-diffusion approximation for charged particle fluxes. Numerical tests are carried out for the discharge in Nitrogen, with GaAs semiconductor layer. We first derived and tested three different fluid models for DC glow discharge: the "simple" model, where the ionization is defined by the Townsend approximation, and two "extended" models with more detailed sets of plasma-chemical reactions. Accuracy and reliability of these models are analyzed by making comparison between the computed and experimental current-voltage characterics. Then, these models are applied to numerical investigation of the gas discharge-semiconductor system. First, the homogeneous stationary states of the system are identified. Then, the analysis of these states allows to develop bifurcation curves in the parameter space, separating the region where the plasma is stable from the region where it performs the homogeneous oscillations. Comparison with the experimental data allows to determine the accuracy and the ranges of applicability of different modelling approaches.