A simulation about the influence of the gate-source-drain distance on the AlGaN/GaN HEMT performance at Ka-band

To improve the frequency and the output power, we present the results on the effect of distance between source-gate-drain in AlGaN/GaN high electron mobility transistors (HEMTs) by silvaco emulator. First, we adopt centrosymmetric gate structure, it means the L_gs(source-gate spacing) is equal to the L_gd(gate-drain spacing), and the L_sd(source-drain spacing)changes from 4μm to 2.4 um. It presents that the drain current, transconductance, the gain at 35GHz, f_T(current gain cutoff frequency)and f_max(maximum frequency of oscillation)get improved with the decrease of L_sd. However, when the distance comes to a certain extent, the fringe scatter from ohmic contact of source and drain would weaken electron mobility in channel layer, and it is hard to improve in technology fabrication. In addition, changing the L_sg and L_dg simultaneously demonstrates the influence of the different gate locations. Finally, we get the range of source-gate-drain distance for Ka-band AlGaN/GaN HEMT by the simulation results.