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Dependence analysis of the GaN HEMT parameters on the thickness AlGaN barrier layer by numerical simulation


V.A. Petrov – Engineer, CJSC “Svetlana – Elektronpribor” (St.-Peterburg). E-mail: V.G. Tikhomirov – Ph.D. (Eng.), CJSC “Svetlana – Elektronpribor” (St.-Peterburg). E-mail:

The use of the mathematical modeling methods, based on the multidimensional numerical models of calculation of the carrier transport, thermal processes and dynamical characteristics helps to add, check and explain existing experimental data. Also behavior of the device structures with changing parameters can be predicted that is difficult to reproduce experimentally. In this work we present the results of numerical modeling of influence of some operating parameters and external impacts on the current-voltage characteristics of field effect transistors – high electron mobility transistor (HEMТ), based on the AlGaN/GaN heterostructures. Prediction of field effect transistor output characteristics requires the model which includes the statistics of carrier distribution in the heterostructure layers, peculiarities of carrier transport and electron mobility in the HEMT channel to account the heating up of the carriers and adequate description of current processes under external impacts. A typical AlGaN/GaN HEMT was selected as the object of our modeling. It consists of a 4H semi-insulating silicon carbide (SiC) substrate. Buffer layer of unintentionally doped (UID) 3 µm-thick GaN, 20 nm-thick AlGaN barrier layer. We have optimized the mathematical models used to analyze the characteristics of our heterostructures in accordance with recom-mendations given in our work. A two-dimensional hydrodynamic mathematical model is used in many industrial simulation systems, which, combined with the original models of the electrons behavior in material media, gives good results. Similar approaches are de-scribed in other works. When selecting a model of electron transport, we take into account the balance between the speed of calculations and the required accuracy. The calculation of the drift-diffusion model does not meet the demands of practice in the calculation of sub-micron transistors. We believe that combining of the Monte Carlo method with the well-established and calibrated hydrodynamic model is the best choice in many cases. We have solved the system of four differential equations in partial derivatives: electric field Poisson\'s equation, current continuity equation, the heat flux and energy balance for the electrons, which are solved self-consistently. This system of equations is supplemented by specific equations for material media - the mobility of the carriers, the electron density, and thermal conductivity. First, we have adapted the numerical models to the features of transistor device design and its technology. Next, the calculation of the static current-voltage and capacitance-voltage characteristics of the HEMT has been done. In this work shows the experimental and calculated static current-voltage characteristics of the modeled AlGaN/GaN HEMT. The very good agreement of modeling results and experimental data were achieved.


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