Enhanced mobility via diluted polarization in graded AlGaN/GaN systems

This study investigates the influences of a graded AlGaN barrier layer on electron mobility in AlGaN/GaN heterostructures. By varying the graded layer thickness, we observed a systematic mobility enhancement from 1300 cm2/V s (abrupt interface) to 2070 cm2/V s at an optimal thickness of 10 nm. Beyond this threshold, mobility decreased due to the transition from two-dimensional electron gas conduction to three-dimensional parallel conduction, as confirmed by capacitance–voltage (C–V) measurements. The observed mobility enhancement is attributed to the suppression of Coulomb and alloy scattering facilitated by polarization dilution within the graded layer. Furthermore, fabricated AlGaN/graded barrier/GaN field effect transistors with a source–drain spacing of 20 μm exhibited a significant reduction in on-resistance, approximately 40% lower than conventional abrupt heterostructures. These findings highlight the potential of graded AlGaN barriers in optimizing carrier transport for next-generation high-electron-mobility transistors.