Influence of the Al mole fraction on microwave noise performance of AlxGa1-xN/GaN HEMTs

To reveal the influence of Al mole fraction on the microwave noise performance of Al_xGa_1-xN/GaN HEMTs, numerical analysis is performed on the intrinsic noise by reducing its value from 35% to 25% and 15% in this paper. A model based on measurement results is used and simulations are carried out by commercial TCAD soft Silvaco Atlas. The I-V curves and both of the gate and drain noise spectral density are calculated and compared at different bias. The results show that the reduction of the Al mole fraction degrades the intrinsic microwave noise behavior of HEMT´s only at high bias currents due to the poor carrier confinement. The AlGaN/GaN HEMTs with 25 % Al content has the best minimum noise figure (F_min) at low bias currents due to the reduction of gate noise, and it has the same F_min with 35% at a few higher bias current.