Impact of high-k dielectrics on enhancement-mode AlGaN/GaN MISHEMTs: performance comparison with various buffer layers for RF power electronics

Abstract

This research article investigates the performance implications of incorporating high-k dielectric hafnium oxide (HfO₂ ≈ 25) in enhancement-mode AlGaN/GaN high electron mobility transistors (HEMTs) with various AlGaN barrier mole function of 0.17 and 0.25 for high-speed RF power electronics using silicon carbide (SiC) substrate. This study also explores the influence of different buffer layer materials, such as AlGaN and β-Ga₂O₃ on device characteristics and reports a comparative analysis of DC and RF performance metrics. The use of a SiC substrate and buffer layer in GaN HEMTs significantly enhances device performance by increasing breakdown voltage, improving thermal stability, reducing defects and enhancing electron transport. The proposed heterostructure device Al_0.25Ga_0.75N/GaN with β-Ga₂O₃ buffer layer exhibited significantly higher drain current (I_D) of 2.67 A/mm, transconductance (g_m) of 1.204 S/mm, cut-off frequency (f_T) of 32.4 GHz, breakdown voltage (V_BR) of 1378 V compared to Al_0.25Ga_0.75N/GaN with AlGaN buffer HEMT. The proposed device drain current is 17% higher than the AlGaN buffer HEMT. The improved performance of devices with a SiC substrate and buffer layer opens new possibilities in various fields, such as power electronics, RF amplifiers, communication devices, aerospace, and defence applications.