Effect of width scaling on RF and DC performance of AlGaN/GaN-based Ku-band multi-finger 250 nm high electron mobility transistor technology

Abstract

Radio-frequency (RF) high-power high electron mobility transistors (HEMTs) are fabricated with multiple fingers and larger widths to increase the output delivered power. The increased power handling capability is a consequence of the increased capability of handling a larger drain-to-source current. The current is distributed over multiple fingers to keep the current and power density low to avoid heating effects. The width of the devices is also kept preferably long to avoid an excessively large number of fingers and fabrication challenges. However, despite the necessity of maintaining the linear scaling of output power with an effective total width, nonlinearity and non-scalability are intrinsically present. This non-ideality happens due to the aperiodic nature of the multiple-finger device structures and their response to RF signals. This work investigates the effect of varying widths and the variable number of fingers on the DC and RF performance of AlGaN/GaN HEMTs. HEMTs with appropriate sizes are fabricated and characterized. The DC characteristics mostly scale linearly with width (W) and the number of fingers (n). Contrary to the DC performance, the RF characteristics do not linearly scale with W and n but degrade after some threshold value for W for a given n and input power.