Ultra-high permittivity BaTiO3 (<i>ε</i> = 230) on Al2O3/AlGaN/GaN MISHEMTs for field-management in high-voltage RF applications

We report ultra-high permittivity of RF sputtered BaTiO3 films on AlGaN/GaN Metal–Insulator–Semiconductor High-Electron Mobility Transistors (MISHEMTs) via high temperature sputtering and subsequent annealing in nitrogen. We developed a novel dielectric deposition methodology, which enables high permittivity for field management while maintaining good off-state characteristics utilizing a combination of room temperature and elevated temperature depositions of sputtered BaTiO3. The layers are characterized with transmission electron microscopy to show a desirable amorphous Al2O3 layer and a polycrystalline ultra-high permittivity BaTiO3 layer. A relative permittivity of 230 is extracted via C–V, and the gate–drain breakdown increased vs the control from 67 to 162 V (5 mA/mm ID compliance) in the sample with high-κ BaTiO3 and room temperature interlayer. It is demonstrated via small-signal RF measurements that BaTiO3 permittivity does not markedly decrease at high frequencies and dielectric loss does not substantially increase. The results of this study characterize the dielectric material depositions toward a path forward for high-κ BaTiO3 dielectric integration with Al2O3/AlGaN/GaN MISHEMTs, which will fully utilize the field strength in GaN for high-voltage radio frequency and power electronics applications.