Modeling and simulation of oxide dependent 2DEG sheet charge density in AlGaN/GaN MOSHEMT

摘要

Oxide dielectric present in metal oxide semiconductor high electron mobility transistor plays an important role during formation of two dimensional electron gas (2DEG). The sheet charge concentration (n(s)) is dependent on the Eigenenergy states present in triangular quantum well at AlGaN/GaN interface. The energy states are in fact functions of vertical electric field at the edge of the well. Therefore in this paper a model is developed to find out Electric field and flat-band voltage (V-T) by adopting energy band approach to incorporate oxide parameters in it unlike the conventional method of solving Poisson's equation, which is the uniqueness of this paper. The Eigenenergy states are dependent non-linearly on electric field. In the present case, three quantum states in the well are considered along with the Fermi-Dirac distribution function to obtain . The dependence of 2DEG density, electric field and flat-band voltage on the oxide parameters such as thickness and electrical permittivity is analyzed. With respect to thickness in SiO2 and Al2O3. n(s) shows inverse relationship; whereas in HfO2 it is direct due to positive charges accumulated at oxide/barrier interface. To the best of author's knowledge the work is first of its kind and due to lack of experimental data; the obtained results are compared with TCAD results to validate the model.