Study on epitaxial structure and substrate material variations for improving electrical reliability of the MSM AlGaN/GaN 2DEG varactors

The metal–semiconductor–metal (MSM) aluminum gallium nitride/gallium nitride (AlGaN/GaN) two-dimensional electron gas (2DEG) varactor has electrical characteristics that its capacitance can decrease sharply as applied bias exceeds the threshold voltage. By actual fabrication and measurement, we explore the effects of electrode design on the electrical properties of the varactor and verify its application in an anti-surge circuit. In this study, based on previous results, we further vary the wafer structure and substrate material and prepare the GaN-on-silicon, GaN-on-sapphire, special GaN-on-sapphire wafers with three different Al_0.26Ga_0.74N barrier layer thicknesses (22, 33, and 44 nm) as well as double-2DEG GaN-on-sapphire wafers for manufacturing various MSM varactors to determine dependent electrical properties and improve signal transmission efficiency in the radio frequency (RF) application field. The experimental results provide an effective candidate for resisting and suppressing attacks such as a malicious electromagnetic pulse.