In this paper, the performance of AlGaN/GaN HEMTs with different gate-to-source length (L-GS) and with a fixed distance of drain-to-source (L-DS) is presented. The increase in L-GS makes the source resistance (RS) increase. In general, the larger the resistance, the better the linearity and stability in the power amplifier, thereby these devices were used to study and compare the device characteristics. According to output 3rd order intercept (OIP3), there is no linear trend in the linearity with related to the L-GS and R-S. The optimal layout for the different geometry in this study is the device with gate width of 250 mu m and LGS of 1.325 mu m.