Influence of diverse dielectric materials on the performance of enhancement-mode AlGaN/GaN MISHEMTs with a β-Ga2O3 buffer and substrate for RF and power applications

Abstract

In this study, we have investigated the influence of diverse dielectric materials on the performance of enhancement-mode AlGaN/GaN MISHEMTs using a β-Ga₂O₃ buffer and substrate. By employing a range of dielectrics (SiO₂ (ε_r = 3.9), SiN (ε_r = 7.5), Al₂O₃ (ε_r = 9.8), HfO₂ (ε_r = 25), La₂O₃ (ε_r = 27), and TiO₂ (ε_r = 80)) for gate oxide and surface passivation, we aimed to explore their effects on device characteristics and identify trade-offs associated with their implementation. β-Ga₂O₃ has a wide bandgap (4.8 eV for β-phase), which is compatible with GaN (3.4 eV).The β-Ga₂O₃ substrates and the buffers can potentially be produced in larger sizes with good wafer quality and fewer defects compared to traditional GaN buffers and other substrates such as sapphire or silicon carbide (SiC). The dielectrics SiO₂ (TiO₂) delivered a drain current of 2.54 (2.79) A/mm, a transconductance of 0.33 (0.54) S/mm, a cut-off frequency of 47 (21) GHz for a drain voltage 20 V, an ON resistance of 1.56 (0.96) Ω mm, a breakdown voltage of 1012 (1906) V, and an intrinsic time delay of 0.84 (0.68) pico-seconds. The proposed device with a SiN (ε_r = 7.5) insulator exhibited the highest JFOM (V_BR × f_T) of 50.34 THz-V. This study paves the road for selecting the appropriate insulator for next-generation RF and power applications.