Linearity improvement in AlGaN/GaN HEMTs using longitudinally-varying gate recess

Abstract This paper reports an effective way of improving the linearity of AlGaN/GaN High Electron Mobility Transistors (HEMTs) by modulating the AlGaN barrier thickness under the gate electrode along its width. This produces an offset in the local equivalent threshold voltage (VT ), and consequently, the proposed device acts as multiple transistors with a VT offset connected in parallel configuration. Due to the resulting gm3 cancellation, the new device
structure exhibits 10-fold suppressed gm3 peak compared to conventional planar-gated AlGaN/GaN HEMTs. A linearization of Cgs −VGS curve is also demonstrated. Compact modeling and large signal simulation of the proposed device exhibits 7 dB improvement in the linearity figure-of-merit, OIP3/PDC at 5 GHz, compared to the conventional planar gated devices. Additionally, around 10 dB suppression in two-tone third-order intermodulation distortion (IMD3) and improved efficiency across 3 dB, 6 dB and 10 dB output back-offs (OBOs) is observed compared to the conventional planar-gated AlGaN/GaN HEMTs at 5 GHz for deep class AB applications. Hence, the proposed longitudinally-varying gate recess technology is a promising candidate for mm-wave linear and efficient amplifiers, suitable for 5G applications.