RF linearity and improved transconductance of ScAlN/GaN HEMT with novel inverse L-shaped gate structure.

• An asymmetric gate design incorporating an AlGaN cap on ScAlN/GaN HEMT demonstrates a flat g m profile and significantly reduced g m derivative, leading to improved linearity of GaN-based transistors. • HEMTs with air cavity design is comprehensively studied in detail. • Describing the influence of ScAlN layer thickness on device frequency, we analyzed how the ScAlN layer increases device frequency and linearity. • The effect of the thickness and aluminum composition of the AlGaN cap layer on the linearity of ScAlN/GaN HEMTs with asymmetric gate design is described. In this study, we investigate the enhancement of effective transconductance and gain linearity in submicrometer gate AlGaN-barrier-based transistors utilizing ScAlN/GaN coupling-channel structures. A novel asymmetric gate design, incorporating an AlGaN cap on ScAlN/GaN HEMT, is proposed. This configuration demonstrates a flat transconductance profile and significantly reduced transconductance derivative, thereby improving the linearity of GaN-based transistors. For transistors with a gate length of 0.5 μm, both the current gain cut-off frequency and power gain cut-off frequency are measured at 53.52 GHz and 72.98 GHz, respectively. These values represent a more than threefold increase from the corresponding frequencies of conventional devices. Moreover, the theoretical Output Third-Order Intercept value of the proposed structure has increased by 7.5 dBm compared to conventional HEMTs. This superior linear performance can be attributed to the combined effect of AlGaN cap layer and air cavity. Furthermore, the introduction of the ScAlN layer results in a substantial impact, including a decrease in electron concentration from 4.96 × 10¹⁹/cm³ to 1.98 × 10¹⁹/cm³ and an increase in electron velocity from 4.5 × 10⁷ to 7.6 × 10⁸ cm/s. These findings underscore the potential of the proposed device for high-frequency applications requiring superior linearity. [ABSTRACT FROM AUTHOR]