GaN HEMTs using Si-rich SiN passivation interlayer (original) (raw)

In this work, we report GaN high-electron-mobility-transistors (HEMTs) on SiC with gate lengths of various dimensions for optimum performance. 125 µm gate width, 4 µm drain source spacing AlGaN/GaN HEMTs with gate lengths of 0.3, 0.6, 0.8, and 1.0 µm were fabricated. For devices with the gate lengths in the range of 0.3-0.8 µm, with an increase in gate length, the output power density (P out) at 4 GHz is increased from 1W/mm to 1.5W/mm, although the I ds,max , g m , f t and f max values are decreased in acceptable limits. The great enhancement in P out with the increase in the gate length is due to fact that the increase in gate length affects the controllability of the electric field under the channel; hence the peak value of the electric field under gate contact decreases and the electric field variation under the gate contacts is smoother. For the device with the gate length of 1.0 µm I ds,max , g m values are almost the same as the values with the gate length of 0.8 µm, but P out is decreased, since with this gate length the increase in parasitic capacitances is more effective and this limits the improvement due to the gate length increase.