Epitaxial BaTiO3 thin films directly integrated on AlGaN/GaN heterostructures with low dielectric loss

GaN-based high-electron-mobility transistors (HEMTs) are well-suited for high-power and RF device applications due to the excellent transport characteristics and high breakdown field of GaN. However, the technology is inherently limited by high and non-uniform peak electric fields at the drain-edge of the gate that causes premature electric field induced breakdown. Recently, electric field profile management strategies have been proposed utilizing high permittivity (εr) dielectric materials, such as BaTiO3 (BTO). These dielectric BTO layers are typically deposited using techniques such as RF magnetron sputtering, which produces disordered films with lower permittivity values and interface quality. Here, we present an approach to create epitaxial BTO films on a GaN HEMT structure by use of oxide molecular beam epitaxy and employing thin SrTiO3 and TiO2 buffer layers to promote BTO crystallinity. We investigate the effect of BTO deposition temperature on both structural and electrical properties and find a correlation between crystal quality and permittivity, with a BTO film deposited at 850 °C exhibiting an extracted effective εr = 228 and loss tangent value of 2.7 × 10−3 at 10 kHz. These results offer an approach to designing a GaN HEMT structure with high-quality integrated high-εr dielectrics capable of enhanced RF and power-switching performance.