Modeling of 2DEG sheet carrier density and DC characteristics in spacer based AlGaN/AlN/GaN HEMT devices

Abstract

In this paper, 2-D physics based model for two-dimensional electron gas (2DEG) sheet carrier density ns and DC characteristic of the proposed spacer layer based AlxGa1−xN/AlN/GaN High Electron Mobility Transistors (HEMTs) is modeled by considering the triangular quantum well. To obtain charge density ns, the variation of Fermi level with supply voltage and the formation of Energy sub-bands E0, E1 is considered. The obtained results are simple and easy to analyze the sheet charge density, DC characteristics model for spacer layer based AlxGa1−xN/AlN/GaN HEMT power devices. Due to large two-dimensional electron gas (2DEG) sheet carrier density and high velocity, the maximal drain current density achieved is very high. An expression for the two-dimensional electron gas (2-DEG) charge density ns, valid in all regions of device operation is studied and applied to derive drain current along with channel length modulation and velocity saturation effects. The spacer layer based AlGaN/AlN/GaN heterostructure HEMTs shows excellent promise as one of the candidates to substitute present AlGaN/GaN HEMTs for future high speed and high power applications. The proposed model is in a good agreement with experimental data for analyzing both sheet carrier density and drain current over a range of applied voltages and different gate geometries.