3D Simulation on Polarization Effect in AlGaN/GaN HEMT

In this paper, we investigated the polarization effects on the electrical and structural characteristics of AlGaN/GaN HEMT. Both the Al mole-fraction and the barrier thickness of AlGaN, which determine the profiles of a two-dimensional electron gas, were simulated to obtain the optimum HEMT structure affecting the polarization effect. As a results, we found that the amount of bound sheet charges was increased by 16% and the maximum drain current density (,max) was increased by more than 37%, while AI mole fractions are changed from 0.3 to 0.4. We also observed a 37% improvement in maximum drain current density (,max) by increasing AIGaN layer thickness from 17 to 38 nm. However when AlGaN layer thickness reached the critical thickness, DC characteristics were dramatically lowered due to 'bulk' relaxation in AlGaN layer.