Performance Analysis of AlGaN/GaN HEMTs with InGaN and Graded InGaN Back-Barrier Structures

This work presents a comprehensive performance analysis of Al0.35Ga0.65N/GaN high electron mobility transistors (HEMTs) on a SiC substrate incorporating uniform InGaN and compositionally graded InGaN back-barrier (BB) structures. The proposed architectures aim to enhance vertical carrier confinement, suppress buffer leakage, and improve both DC and RF characteristics through band structure engineering. Detailed TCAD simulations incorporating polarization effects, composition-dependent bowing parameters, advanced carrier transport, trap dynamics, and self-heating models are employed for accurate device evaluation. The graded InGaN back-barrier structure demonstrates superior performance compared to the conventional uniform InGaN BB. The device exhibits enhanced drain current (~3.7 A/mm), higher peak transconductance (~1.5 S/mm), and improved cut-off frequency (~180 GHz), representing nearly 20% enhancement in RF performance. Parasitic capacitances, particularly gate–drain capacitance, are reduced due to stronger vertical electron confinement. Furthermore, the graded structure achieves a steeper subthreshold slope (24.3 mV/dec), lower DIBL (43.34 mV/V), and significantly improved breakdown voltage (~54 V), indicating enhanced electrostatic control and high-voltage reliability.