Investigation of performance enhancement of a recessed gate field-plated AlGaN/AlN/GaN nano-HEMT on β-Ga₂O₃ substrate with variation of AlN spacer layer thickness

In this research article, a recessed field-plated gate AlGaN/GaN-based nano-high electron mobility transistor (HEMT) grown on a β-Ga₂O₃ substrate is designed with and without insertion of AlN layer between AlGaN and GaN layers. The impact of intended AlN layer on the proposed HEMT’s carrier transport features, DC, and RF characteristics are discussed in this study. The outcome shows that introducing a thin AlN spacer layer induces the location of two-dimensional electron gas (2DEG) to shift away from AlGaN/GaN interface. Furthermore, the influence of different AlN thicknesses is studied. It has been observed that the 2DEG concentration rises as AlN layer thickness increases. In general, the mobility of 2DEG is reduced in typical HEMTs due to scatterings induced by alloy and interface roughness. The outcomes demonstrated that a 2 nm-thick AlN layer exhibited the least amount of interface scattering, which results into highest charge carrier mobility. The proposed nano-HEMT demonstrated an enhanced transport, DC and RF properties with the utilization of a lower lattice mismatched β-Ga₂O₃ material as a substrate, and the positioning of an AlN layer of thickness 2 nm between upper Al_0.3Ga_0.7N barrier and GaN buffer layers.