Effect of heterostructure parameters and fabrication technology on the noise properties of AlGaN/GaN HEMT

The paper presents the results of investigation of noise parameters of AlGaN/GaN HEMT manufactured on various heterostructures and in accordance with varied technological routs. It was proved, theoretically and experimentally, that a decrease of the thickness of AlGaN/GaN heterostructure barrier layer down to 10 nm and less leads to a corresponding decrease of the noise coefficient. This fact in connection with the temperature researches of the noise coefficient described in literature reveals significant difference of AlGaN/GaN HEMT heterostructure channel noise generation mechanism compared to that of traditional GaAs HEMT. It is possible to manufacture GaN HEMT with noise coefficient significantly lower than in GaAs HEMT by means of optimization of the ratio between the heterostructure barrier layer thickness and T-gate length using maximization of f_T²R_ds value. From the technological aspect along with the layer design the AlGaN/GaN heterostructure surface roughness minimization, due to its influence on the carriers scattering, and T-gate profile in terms of C_gd minimization should be taken into account.